Which of the Following Would Be an Example of Applied

Which of the following would be an example of applied research?

A) Studies of the earth's climate 5,000 to 6,000 years ago.
B) Research into the use of new combustion techniques that could increase gas mileage in vehicle engines.
C) Research into the effects of zero-gravity environments on plant life.
D) Research into string theory in advanced subatomic physics.