Which effect do rapidly cooling temperatures have on the water cycle?
A: Water vapor condenses into droplets.

In the human kidney, urea from the blood is filtered through the glomerular membrane into a nephron. The movement of urea across this membrane occurs without an input of energy. Which factor is the most likely reason urea absorption does not require energy?
A: a concentration gradient

A scientist uses angstrom units to measure the distance between two points. The scientist is most likely measuring the distance between two
A: atoms.

Which a molecular process found only in retroviruses?
A:
reverse transcription