Question

During aerobic cellular respiration, what combines with hydrogen ions and the product is released as a by-product of respiration.
a. ADP
b. carbon
c. oxygen
d. acetyl CoA

Answer 1

 The correct answer is C, Oxygen.
During aerobic cellular respiration, oxygen combines with hydrogen ions and water is released as a by-product of respiration. 

Explanation; 
Cellular respiration allows organisms to release energy stored in chemical bonds of glucose, and other nutrients. The energy in glucose or other nutrients such as fats is used to produce ATP, which cells use to supply their energy needs. During aerobic respiration (in presence of oxygen), oxygen is reduced and water is produced together with carbon dioxide as by-products. 

Answer 2

The right answer here is C, during aerobic cellular respiration it is oxygen that combines with hydrogen ions and then later releases water as a by-product of respiration.