Will an egg float higher in water with more salt

What are genotypes? what are phenotypes?

Hurry which of these is true about index fossils? a) are very scarcely found b) used as guides in relative dating c) found in the youngest layer of the rock d) used as reference points in absolute dating

Which is the function of the hypothalamus in thermoregulation? answers: -sensor -effector -stimulus -intergrating center it's either a or c i believe