If two chromosomes of a species are the same length and haved similar centromere placements and yet are not homologous, what are they?

Non-homologous chromosomes

Explanation:

The overall length of the chromosomes and the placement of centromere are the two factors that required to same within the two pairs of chromosomes these chromosomes are considered as homologous chromosomes.  

The non-homologous chromosomes can be defined as chromosomes that do not have the same overall length and placement of centromere is also not same. These chromosomes do not belong to the same pair or do not appear in the same pair.

The time of replication and banding pattern varies considerably in the non-homologous chromosomes.

hey, i believe your answer would be d. sugar ribose and the base uracil. i believe this is the answer, because rna consists of sugar ribose, adenine, guanine, cytosine, and uracil.

your first option is incorrect, because that's dna. where it consists of sugar deoxyribose, adenine, guanine, cytosine and thymine.

your second option is also incorrect, this is because sugar deoxyribose is in dna, and uracil is in rna. these two do not make sense together.

your third option being incorrect, because sugar ribose is in rna, but not the base of thymine. rna consists of uracil, not thymine.

lastly your fourth option being correct! this answer is correct, because both sugar ribose, and the base uracil are in rna! ~

answer is d. sugar ribose and the base uracil.