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

In a monohybrid cross, when $F_1$ is crossed with a homozygous dominant parent, what type of offspring will be obtained?

Which statement is incorrect regarding $Drosophila$ $melanogaster$?

How can the concept of dominance be explained?

Mating of an organism to a double recessive in order to determine whether it is homozygous or heterozygous for a character under consideration is called

Given below are two statements:
Statement $I$:
Mendel studied seven pairs of contrasting traits in pea plants and proposed the Laws of Inheritance.
Statement $II$:
Seven characters examined by Mendel in his experiment on pea plants were seed shape and colour,flower colour,pod shape and colour,flower position and stem height.
In the light of the above statements,choose the correct answer from the options given below: