Respiration involves the breakdown of sugar. this process results in the production of energy for the cell. in order for cells to produce the most energy, what gas should be present?
a) oxygen
b) nitrogen
c) water vapor
d) carbon dioxide

The answer is letter A. In most organisms cellular respiration usually involves oxygen to produce the most energy. Except in the process of fermentation, where the cells are deprived with oxygen causing it to form bacteria and other forms of organisms within the fermented sample.

The answer is b hope this

An autotrophic protist - they can perform photosynthesis and mainly consist of unicellular algae. they can be divided into number of systematic group according to the shape of their cell and the type of photosynthetic pigments they use.