| Date | November 2015 | Marks available | 1 | Reference code | 15N.1.SL.TZ0.20 |
| Level | Standard level | Paper | Paper 1 | Time zone | TZ0 |
| Command term | Question number | 20 | Adapted from | N/A |
Question
The diagram represents the carbon cycle.
Which process has the greatest relative role in transferring carbon?
A. Decomposition
B. Combustion
C. Photosynthesis
D. Cell respiration
Markscheme
C
Examiners report
There have been some complaints about the use of the word "relative" before role. Although this word was not needed, it does not invalidate the answer to the question. This question had a very low discrimination index and only 40% of the candidates were able to answer this question correctly. The answer was quite easy, as one can see all arrows leaving from carbon dioxide in the atmosphere and the only arrow going back to carbon dioxide in atmosphere is the one coming from photosynthesis, therefore this must be the most important as it is equivalent to the addition of all the other arrows in order to balance the cycle.
