Variation stands for differences in traits of progenies from

Match the terms in Column-$I$ with their descriptions in Column-$II$ and select the correct option.

Column-$I$	Column-$II$
$(A)$ Dominance	$(1)$ Many genes govern a single character.
$(B)$ Co-dominance	$(2)$ In a heterozygous organism, only one allele expresses itself.
$(C)$ Pleiotropy	$(3)$ In a heterozygous organism, both alleles express themselves fully.
$(D)$ Polygenic inheritance	$(4)$ $A$ single gene influences many characters.

Differentiate between a monohybrid cross and a dihybrid cross.

$A$ back-cross is a cross between ........

Select the correct option for the following statements:
$P - F_1$ generation shows traits of both parents.
$Q - F_1$ generation shows a new trait (intermediate).
$R - F_1$ generation shows only one of the two parental traits.
$\quad \quad P \quad Q \quad R$

Which one of the following is not a parasitic adaptation?