One major cause of floods is
a. rapid spring snowmelt.
b. light rain over a large area.
c. a decrease in stream discharge.
d. increased capacity of stream channels

The answer is A. Rapid Spring Snowmelt

Light rain over a large area simply not gonna causing any flood. Rapid spring snowmelt on the other hand is one of the major cause of floofs. Snow is basically a water which take forms in a more solid substance. If the snow is located in higher grounds, it tend to send flood to the lower ground when it melts.

Thats why we usually evaporate it through heat. One of the area in the united states that suffer from Rapid Spring Snowmelt is Alaska.

The answer is d., a mountain.