Which term describes a type of trait that is usually expressed only when an organism has 2 identical alleles for the trait?
a. heterozygous < < < <
b. dominant
c. homozygous < < < <
d. recessive
im stuck between these 2.

The right type of trait is D. recessive.

The terms recessive and dominant are traits (or characters) that relate to alleles.

Homozygosity and heterozygosity characterize individuals. But in the question we are looking for a type of trait (so the answer should not be either of these two).

An allele is dominant if present on only one of the two homologous chromosomes (one of paternal origin, the other of maternal origin), it is capable of expressing a character. Thus it expresses its character that it is present on the two chromosomes of the pair or on only one. An allele is recessive if its expression requires its presence on both homologous chromosomes (in the homozygous state). A dominant allele masks the presence of a recessive allele (in the heterozygous or homozygous state).

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.