Answer the following question given this paragraph: 

Gas exchange is needed to provide cells with the oxygen they need for cellular respiration. Cells cannot survive for long without oxygen. Gas exchange is also needed to carry away carbon dioxide waste. Some of the carbon dioxide in the blood dissolves to form carbonic acid, which keeps blood pH within a normal range.


Q: What is needed to provide cells with the oxygen they need for cellular respiration?

 Choices:

- vascular tissue

- passive transport

- photosynthesis

- gas exchange

A:
gas exchange
