Originally prescribed in the late 1950s as a morning sickness pill, scientists soon realized that the drug thalidomide was causing babies to be born with a condition called phocomelia, involving the malformation of limbs during fetal development. Within 5 years of its introduction, the drug was pulled from the market because of the evidence that it was a(n) .

the drug was pulled from the market because of the evidence that it was a(n) teratogen

Explanation:

Teratogens are drug or other agents that cause physical or functional bnormalities in fetuses that are exposed to such agents. A typical example is alcohol. The degree of the abnormality on the fetus depends on a number of factors which are:

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.

the cell cycle is the final answer! : )