Most biologists believe that -there are more commensal relationships than we think -there are no true parasitic relationships in nature -animals are probably harmed or by commensalism in subtle ways - animals most likely benefit from parasitic relationships in unknown ways

The right answer is C.

Classically positive interactions or facilitators between species are divided into two broad categories:

- those where the two partners involved benefit from each other: the mutualisms (symbolized by + / +)

- those where one of the two partners makes a profit or an advantage while the other gets nothing from it without being affected negatively: it is the commensalism symbolized by + / 0.

It may be that bacterial commensalism has an interest in its host (the animal) in the sense that it protects against parasites, or on the contrary, it favors their appearance.

from the original order (top to bottom) the new order will go

1 (founder)

4 (hawk)

2 (mutate)

3 (next generation)

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.