Which experimental design decision would most likely produce invalid and unreliable results

Amouse that is homozygous for the dominant trait has the genotype . it has . a mouse that is homozygous for the recessive trait has the genotype . it has . image of fur color of mice

Hummingbirds drink nectar from flowers, while robins eat plant seeds. what does this reduce?

Ihave no idea how to solve these. plus there's another question that is 2) a 10 kilogram meteorite is collected in space and brought back to earth. it is composed of 1.25 kg of uranium-238 and 8.75 kg of lead-206. how many u-238 half lives have passed? what is the approximate age of the meteorite?