Alan observed that a lot of soil from his garden swept off from after heavy rain. Which is this process called? A.)groundwater recharge
B.)snow melt
C.)infiltration
D.)surface runoff

D.) Is the most sensible answer.

Explanation: I used the process of elimination to solve this. Groundwater recharge sounds too far off of the topic, snow melt is...well...melting snow, infiltration also has nothing to do with the subject, but surface runoff is the only one that makes sense, is on topic, and seems to have a meaning similar to the occurrences describes in your question.