Given below are two statements:

Statement I - Back cross is the crossing of $F_1$ hybrid with one of the two parents from which they were derived.

Statement II - Test cross involves the crossing of $F_1$ - hybrid with its homozygous recessive parent.

In light of above statements, choose the correct answer from the option given below.

Monohybrid crosses are useful in demonstrating which of the following laws of inheritance suggested by Mendel?

Which of the following statements are correct?

i. $X$ chromosome has large amount of euchromatin.

ii. heterochromatin is genetically inert.

iii. Both X and Y chromosomes are homologous.

iv. Crossing over does not take place in sex chromosomes in female.

Choose the correct option.