An angiosperm plant having red coloured flowers when crossed with another having the same colour produced $40$ progenies,out of which $30$ plants were with red coloured flowers and $10$ plants were with white coloured flowers. Find out:
$(a)$ What is the possible genotype of parent plants?
$(b)$ Which trait is dominant and which is recessive?
$(c)$ What is this cross called and what is its phenotypic ratio?

(A) The parent plants must be heterozygous $(Rr)$ because they produced white-flowered offspring $(rr)$,which is only possible if both parents carry the recessive allele.
$(b)$ Red colour is the dominant trait because it appears in the majority of the progeny $(30/40)$,while white colour is the recessive trait as it only appears in the homozygous recessive condition $(10/40)$.
$(c)$ This is a monohybrid cross. The phenotypic ratio is $30:10$,which simplifies to $3:1$ (Red:White).