Question to you: What is something cells cannot survive without?
Options:
- (A) gas
- (B) Air
- (C) O2
- (D) CO2
- (E) Ca
- (F) O3
- (G) Fe
- (H) He.
Let's reason step-by-step:
Cells cannot survive without oxygen. And oxygen, O2, is the molecule to do it. Cells cannot survive without O2. Final answer: (C).