How many pairs of contrasting traits did Mendel select for his experiments (in $pairs$)?

$A$ test cross is defined as:

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.

Who coined the term 'Genetics'?

Which of the following traits of garden pea studied by Mendel is a recessive trait?

Define and design a test cross.