The air spaces in the leaf interior
a. block gas exchange between the mesophyll cells and the environment.
b. make the leaf weigh more than a leaf packed tightly with cells.
c. make the leaf weigh less than a leaf packed tightly with cells.
d. carry out most of the photosynthesis in the leaf.
C. They help with gas exchange, and the air taking up the space is lighter than the cells that could be there instead. Also, only cells can carry out photosynthesis, not air.
