whats the diffrence between cellular respiration & fermentation?

Cellular respiration is an aerobic process, which requires oxygen at the end. It starts with glycolysis (glucose is degraded to pyruvate, 2 ATPs formed), followed by the TCA cycle and oxydative phosphorylaton in mitochondria (oxygen is used as a terminal electron acceptor). Overall, a lot of energy (38 ATPs) are formed from 1 glucose during the respiration.

If there is not enough oxygen, then the cells have to make ATP by fermentation, which follows glycolysis. In this case pyruvate does not enter the TCA, but is converted either to lactate (in muscle cells) or alcohol (for example, in yeasts). Only 2 ATPs are generated, but the reduced coenzymes (NADH) are regenerated (recycled) to be used again in glycolysis.

If you run or exercise a lot, your blood flow cannot supply enough oxygen to the muscles, so the lactic acid will be formed in fermentation, and your muscles will be sour.

Cellular respiration is aerobic. does need Oxygen.

But not fermentation

cellular respiration produces co2, fermentation produces alcohol and lactic acid (sometimes).

your test book will do it for you