Plants cannot directly incorporate nitrogen (n2) into organic compounds. they depend on to make nitrogen available to them.

 "the atmosphere" ;  

            or, more specifically;  the "nitrogen gas from the Earth's atmosphere";
                                                   {" N₂ gas in the Earth's atmosphere" } .

  a. chromosomes are duplicated before cell division so that each new daughter cell has a complete set

The answer would be c, white eyes are homozygous recessive. in the early 1900s, morgan conducted several experiments with vinegar  flies (drosophila). one  sample revealed an anomaly: a  white-eyed, single male fly. he attempted to breed this fly with the typical red-eyed females. the offspring were all red-eyed. using flies from this new generation (brother-sister pairs)  produced some red-eyed and a few white-eyed flies. the white-eyed were all male. in later experiments, he was able to produce white-eyed females. this proved that white eyes are not lethal to either sex (ruling out a and b). since the percentage of white eyes to red eyes is so low, white eyes are not a dominant trait. it would be a recessive trait.