All of the listed human actions affect the nitrogen cycle with the exception of the a) use of agricultural fertilizers. b) runoff of pesticides into streams and lakes. c) production of sewage and animal wastes from farms. d) removal of soil bacteria from irrigation or construction.

The correct answer is option B) runoff of pesticides into streams and lakes.

Explanation:

The nitrogen cycle is the process in which atmospheric nitrogen is fixed to the soil naturally. Agriculture fertilizer is help in adding nitrogen to the soil directly that affect the nitrogen cycle positively.

The nitrogen cycle also affected by the waste and sewage farming as it produces the nitrogen by the process of decomposing. this is also affecting the nitrogen cycle positively. Removal of the bacteria from the soil by irrigation also affects the nitrogen cycle.

Thus, the correct answer is option B) Runoff of pesticides into streams and lakes.

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.