An example of a grad-school level question?
Which cells help to destroy pathogens such as bacteria that enter the human body?

An example of a grad-school level question?
Infections may be caused by

An example of a grad-school level question?
Malaria is a common disease in many countries. What is the cause of this disease?

An example of a grad-school level question?

Greenhouse gases in the atmosphere trap heat near Earth's surface. Which of these is a greenhouse gas?