The Barr body is observed in

Sex determination in plants is caused by .....

Identify the odd one out:

$A$ family has five girls and no son. What is the probability of having a son as the $6^{th}$ child (in $\%$)?

$(a)$ 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.

In the given figure, the part indicated by $B$ is produced by which process?