The two versions of a trait (character) which are brought in by the male and female gametes are situated on
(a) copies of the same chromosome
(b) two different chromosomes
(c) sex chromosomes
(d) any chromosome
The genes are available in various structures or alleles in a sexually reproducing population. These alleles are situated on various copies of the same chromosomes. In an ordinarily diploid sexually reproducing population like humans, every individual has 23 sets of chromosomes. Subsequently, there are two copies of each chromosome.
One chromosome comes from the father through the male gamete and the other chromosome comes from the mother through the female gamete. After fertilization, the zygote is produced having 23 pairs of chromosomes. Hence, the two versions of a trait are situated on copies of the same chromosome.
Therefore, option (a) is correct.