Q: Answer the question

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

Q: Answer the question

Which cells help to destroy pathogens such as bacteria that enter the human body?

A: white blood cells

Q: Answer the question

It is necessary to add a day to the calendar every four years because

A:
the revolution of Earth is not exactly 365 days.