How have humans affected the environment?

Although the two theories differ on the evolutionary path of dinosaurs, they agree that

Astudent observes a star from two positions of earth in its orbit, in summer and winter, and measures the change in the position of the star. which of these can be best calculated by this method?

Guinea pig coat color is determined by a single gene. the allele for black coat color is dominant to brown. in a cross between twoblack-haired guinea pigs, 20 offspring are born. if both parents were heterozygous, probability would predict that approximately howmany of the 20 offspring would have brown hair?