Which of the following is a sex-influenced character?

State how many of the given statements are correct.
$(1)$ In a dihybrid cross experiment,Mendel obtained a test cross ratio of $1:1:1:1$.
$(2)$ Coupling and repulsion were first explained by Bateson and Punnett.
$(3)$ Klinefelter syndrome is a sex-chromosomal disorder occurring in females.
$(4)$ Mendel selected $7$ pairs of contrasting traits in pea plants to explain his experiments.
$(5)$ The chromosomal theory of inheritance was first proposed by Sutton and Boveri.

In maize, albinism is caused by the effect of:

In a certain plant species,red flower colour is incompletely dominant to white flower colour (the heterozygote is pink) and tall stems are completely dominant to dwarf stems. If a tall pink plant $(TtRr)$ is crossed with a tall white plant $(TTrr)$,which one of the following types of plants would be produced in the offspring?

Hybrid vigour is due to

Milk secretion and beard growth,both the traits are