Punnet squares! Can anyone help I’m struggling!

Explanation In order to set up a dihybrid punnet square you must figure put the parents first.

since the first parent is homozygous that means the alleles are the same and since its dom that means alleles are dom. so they would be RRTT

The second parentis Heterozygous which means the alleles are different. This would be shown as RrTt.

when setting up the punnet square the boxes we use to represent the parents are composed of the possible outcomes. In this case the only outcome for the first parent is RT RT RT RT

The second parent has a bit more variation as the possible combinations are RT rT Rt rt

after writing those what you have left is the possible combinations and their genotypes

I added an attached file of the completed square

For the questions what you have all you have to do is follow the chart made

a) 100% and the possible genotypes are RRTT RrTT RRTt RrTt

b) 0% ad none

c) 0% and none

i believe it would cause an increase of percipitation, though i could be wrong. so i would say b is the answer.