No; some mice may have developed lung cancer in less than 500 days of cigarette smoke exposure.
Answer: B. Water breaks down into oxygen molecules for respiration.
Water is the required for photosynthesis, a process by which plants (terrestrial and aquatic) makes their food by utilizing water as a reactant to produce oxygen and glucose as product. The glucose act as a source of energy for conducting various metabolic processes in plants but oxygen is released in the air.

This oxygen is necessary for terrestrial and aquatic animals for respiration. Therefore, water breaks down into oxygen by the process of photosynthesis, hence water plays important role in respiration in living beings.
Species selection. Species selection is the process by which intrinsic biological characteristics in organisms change depending on the type of environment they're interacting with. In this case, the subsequent generations of the fly lost the ability to fly because their environment didn't require them to use wings for survival, hence they stopped growing them and subsequently lost the ability to fly.
It is the cell’s powerhouse and processes energy for the cell.
I was told to remember it as the main brain or the head honcho.Hope this helps.