Probability of genotype $TTrr$ in $F_{2}$-generation of a dihybrid cross is

Appearance of new combinations in $F_2$ generation of a dihybrid cross proves the law of . . . . . . .

In humans, brown eyes $(B)$ are dominant over blue $(b)$ and dark hair $(D)$ are dominant over red hair $(d)$. A man with brown eyes and red hair marries a woman with blue eyes and dark hair. They have two children; one resembles the man (brown eyes, red hair), and the other resembles the woman (blue eyes, dark hair). What are the genotypes of the man and the woman?

In a cross between $AABB$ and $aabb$,what is the probability of obtaining $AaBb$ in the $F_2$ generation (in $/16$)?

In a dihybrid cross,when $F_1$ plants $(RrYy)$ are self-hybridized,what is the segregation ratio of yellow and green seeds in the $F_2$ generation?

The dihybrid cross is associated with the principle of . . . . . . .