Delete the odd one:

In man, the composition of female destined zygote is

Sex of a human child is determined by

Assertion : In humans, the gamete contributed by the male determines whether the child produced will be male or female.

Reason : Sex in humans is a polygenic trait depending upon a cumulative effect of some genes on $X-$ chromosome and some on $Y-$ chromosome.

How is sex determined in various organism ? Give historical background of sex determination.
 

$(a)$ In humans, males are heterogametic and females are homogametic. Explain. Are there any examples where males are homogametic and females heterogametic ?

$(b)$ Also describe as to who determines the sex of an unborn child ? Mention whether temperature has a role in sex determination.