(b): $XO$ type of sex chromosomes determine male sex in grasshoppers. This type of sex­ determination comes under $XX­XO$ type. Its common examples are cockroaches, grasshoppers and bugs. The female has two homomorphic sex chromosomes $XX$ and is homogametic. It produces similar eggs, each with X­chromosome. The male has one chromosome only and is heterogametic. It produces $2$ types of sperms : gynosperms with $X$ and androsperms without $X$. Fertilisation of an egg by $X$ ­bearing sperm yieldsfemale offspring and by no $X$ sperm yields male offspring. $AA + XXAA + XXAA + XOAA + XO$