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  1. R

    a hard Biology question

    Hey guys, here is one question that I think is pretty hard and is not explained anywhere in the book. I will put it as follows: Which statements explain why injections of vaccine may not provide protection against Vibrio cholerae? 1, V.Cholerae bacteria infect the intestine 2. The toxin...
  2. R

    A question on Biology AS level

    Hello guys, It is suggested that diffusion across walls is different from diffusion across membranes. So if I say, oxygen diffuses into alveoli across squamous epithelium of capillary and across alveolar wall, am I right or wrong ?
  3. R

    AS Biology, a bit confused

    Hi guys. I'm doing chapter 8 at this moment and was confused by the sentence, on page 150, which states' If the protein concentration and rate of loss from plasma are not in balance with the concentration and rate of loss from tissue fluid, there can be a build-up of tissue fluid, called...
  4. R

    About the lock and key model of enzyme

    Hi everyone, I'm studying enzyme at this moment and I want to ask about the lock and key model. In the textbook, the enzyme is described as the lock and the substrates keys, yet I think this description is confusing. I think the logic could also go this way: the enzyme is the key and substrates...
  5. R

    Confused about prevention of Cholera taken by travellers

    Hello everybody. I'm currently learning Chapter 12 in the book written by Fosbery(the recommended Cambridge book), and I find it hard to understand. The book says, as in the last sentence of page 199, that travellers from areas free of cholera to those where cholera is endemic used to be advised...
  6. R

    Biology---- Please help!!!

    Hello everybody. I have been confused by the following question for a long time...Please help The answer for this question is D. But why can't C be right? I thought that stomata are open because of guard cells but not transpiration.
  7. R

    Please help! Chemistry sucks.

    First question The answer, as the mark scheme says, is B. I chose A and got it wrong..Can anybody kindly explain a bit about that please!!! The Second one Could anybody explain how to decide the bond angle in this case? D can be ruled out because N has lone pairs, but for the remaining...
  8. R

    Please help in Further Mathematics, quickly...

    Help please!!!!!! Q1:Find the length of the arc of the parabola x=at^2, y=2at, between the points(0,0) and (ap^2,2ap) Q2: Find the length of the arc of the cycloid x=a(t+sin t), y=a(1-cos t), between the points t=0 and t=pi Does anybody feel the final integral hard to evaluate?
  9. R

    Examiner's report needed

    Can anybody attach AL mathematics 2011 Nov examiner's report below please!! It is missing from the paper section in this site, and I can't download it from the websites provided by some people because my country restricts my access.
  10. R

    Emergent, please help in mathematics

    Emergent, please help! I have no doubt in solving this problem as I have nearly finished the further. Yet I need to make sure I score all the method mark given. for ii), please take a look at the mark scheme as below. Can anybody tell how to use the correct trig formulae to obtain a 3-term...
  11. R

    Biology, please help!

    Could anybody explain why the answer is A? I think the observations of all three are all positive.... And. I think the answer should be C, yet it turns out to be D. Extremely confused though... Although ER and mitochondria are all extremely small, couldn't them be visible by proper staining...
  12. R

    Need your help with Chemistry Paper2 Calculation

    The Question is on Chemistry AS paper2 O/N/2012, 9701/23 Question number one part b) iii). Actually you need not look at it. I am confused at the calculation given by the answer. Now, the question is divided into several parts, let's just say in part a), the question is asking candidates to...
  13. R

    What do I need to do if I were to succeed in Biology and Physics Practical ?

    I am totally a layman for experiments... But I want to get a good result in paper 3 for biology and physics...Can anyone suggest any books for me please. Any suggestion will be appreciated. I am grateful for all you guys' help!
  14. R

    About Chemistry Practical

    Guys, I need you help! I'm going to take chemistry paper 3, namely practical, in 2015, yet I'm extremely unfamiliar with this. My teacher is not very efficient, so I guess I have to rely on myself... Do you guys know any book that could be used as a chemistry practical guide? Or is there any...
  15. R

    Serious question..Help please

    Hello, guys! I need you help again. This year I am going to do self-study on further mathematics, which means I need to do paper 1 and 2 on further mathematics, as well as my other AS subjects examinations, including Alevel Maths. I have studied P3 thoroughly by myself, so all I need to worry...
  16. R

    Several questions about CIE examinations

    Hello, everyone. I'm a Chinese student studying in an international school in China. Last year I was in an relatively poor one, where I took IGCSE exams and A-level Mathematics P1 and S1. I transferred to a better school this year. In my current school, I was asked to study P3 and S1. I have got...
  17. R

    Further Mathematics, please help!!!

    Hi, everybody. I have been studying further mathematics since this year and have met a lot of trouble... Please have a look at the following question: Q1: Find the equation of the tangent to the curve r=e^θ, which is a) parallel to the initial line b) perpendicular to the initial line. Q2...
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