Which of the following statements about C4 carbon fixation is not true?
a. C4 carbon fixation is an adaptation for plants exposed to high light intensity.
b. C4 carbon fixation occurs in more plants than C3 carbon fixation.
c. C4 carbon fixation is more common in areas of high temperatures than C3 carbon fixation.
d. C4 carbon fixation occurs in the inner cells of a leaf rather than the entire leaf.