How many pairs of contrasting characters in pea plants were chosen by Mendel?

$A$ test cross is defined as:

$A$: 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.

$A$ modified allele is equivalent to an unmodified allele when it produces what?

Change of male and female parents during crosses is known as

$A$ common test to find the genotype of a hybrid is by