Pure tall plants are crossed with pure dwarf plants. In the $F_1$ generation,all plants were tall. These tall plants of the $F_1$ generation were selfed,and the ratio of tall to dwarf plants obtained was $3:1$. This is called:

Factors are defined as....

Why was Mendel's work not accepted during his time?

Which of the following did Mendel select for his experiments?

What are the characteristic features of a true-breeding line?

Mendel published his work on the inheritance of characters in $1865$,but it remained unrecognized until $1900$ because:
$(a)$ He could not provide any physical proof for the existence of factors.
$(b)$ His concept of factors as stable,discrete units that controlled the expression of traits did not find acceptance from his contemporaries.
$(c)$ Mendel's approach of using mathematics to explain biological phenomena was considered ahead of its time and unconventional.
$(d)$ Communication was not easy (as it is now),and his work could not be widely publicized.