The correct option is B 18
A) 18 molecules of ATP are required.
B) 3 ATPs are consumed for every carbon dioxide molecule fixed in the C3 cycle. Glucose is a 6 carbon compound. So, 6 x 3 = 18 ATP.
C) 18 molecules of ATP are required during the formation of one molecule of glucose.
D) 2 ATP is sufficient to fix only one carbon dioxide molecule in the C4 cycle.
So the correct answer is '18'.