Differences in twins suggest

Read the following statements carefully $:-$
$(a)$ Linkage is physical association of genes on a chromosome.
$(b)$ In $Drosophila$, genes of body colour and eye colour are tightly linked on $X$-chromosome.
$(c)$ In honey bee a fertilised egg develops as a male $(drone)$.
$(d)$ In grasshopper males have only one $X$-chromosome besides the autosomes.
$(e)$ $Drosophila$ can complete their life cycle in about two months.
Choose the correct option having all correct options.

Sickle cell anaemia has not been eliminated from the African population because

$A$ : Test cross is the tool for knowing linkage between genes.
$R$ : Monohybrid test cross gives two phenotypes and two genotypes.

Which one of the following is a genetically transmitted character?

Which of the following is not a sex-linked trait?