What is a cross between two genotypes or phenotypes where the source of gametes is reversed in one cross called?

Which of the following is a dominant character according to Mendel?

How many true-breeding pea plant varieties did Mendel select as pairs,which were similar except in one character with contrasting traits?

$A$: Mendel proposed postulates like "principles of segregation and principles of independent assortment" after studying seven pairs of contrasting traits in garden pea.
$R$: He was lucky in selecting seven characters in pea that were located on seven different chromosomes.

Select the incorrect statement with respect to a reciprocal cross.

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.