How is dna evidence used to show evolutionary relationships

Why is it important to reduce the number of chromosomes in half when forming gametes for sexual reproduction?

The following hormone had their receptors in the cell membrane except a-insulin b-tsh c-gh d- cortisol

Which set of characteristics best describes sedimentary rock? a) largest type of rock, made of organic matter, hardest type of rock b) often contains layers, forms near sources of water, contains fossils c) least abundant type of rock, made of other rocks, made mostly of minerals d) most abundant type in earth's crust, made of magma/lava, contains no fossils