An adaptation is a change that

a. makes a species prettier to look at
b. makes a species become extinct
c. a species survive
d. prevents a species from surviving

The correct answer for the blank is- C. helps a species survive.

Adaptation can be described as process of change in a living organism according to which the organism becomes better suited to the environmental conditions, leading to increase in the chances of survival and reproduction.

According to Natural selection, an evolutionary theory given by Charle's Darwin, organism that can better adapt in the changing environmental conditions survive and increase their number through reproduction, whereas organisms that can not adapt are eliminated from the population eventually.

Thus, option C) is the right answer.

a- all cells come from pre-existing cells

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.