Question

In human males all the chromosomes are paired perfectly except one. This/these unpaired chromosome is/are (i) large chromosome (ii) small chromosome (iii) Y-chromosome (iv) X-chromosome(a) (i) and (ii) (b) (iii) only (c) (iii) and (iv) (d) (ii) and (iv)

Answer 1

the answer is 3. 
in human males x and y chromosomes are not paired as they are not completely homologous. they are homologous only at small regions. the difference in size also prevents proper pairing.

Answer 2

In human males all the chromosomes are paired perfectly except one. This/these unpaired chromosome is/are (i) large chromosome (ii) small chromosome (iii) Y-chromosome (iv) X-chromosome(a) (i) and (ii) (b) (iii) only (c) (iii) and (iv) (d) (ii) and (iv)