Which of these events is caused by contact forces?

Earthquakes along the San Andreas fault in California.

Explanation:

When the two plates collide with each other, earthquakes occur. The contact between them makes this earthquake possible. The contact forces are responsible for the earthquakes as there is contact between two plates.          The gravitational force is a force that is responsible for elevated tides happening on the east coast or the Jupiter's moons to remain in orbit. But this is not a contact force as there is no contact between themMoreover, Without any contact, the magnetic force is a non-contact as it attracts the pins from a distance.          

7is b8 is d9 is c10 is a11 is d

You would do 1500/4 and the answer is 375