How can the amount of water in lakes generally be after rainfall?

Correct answer: It can increase

The direct answer is C, it can increase. Rainfall adds water to a lake directly and also sends runoff through streams and rivers into the lake. If the amount entering is greater than the amount lost through evaporation, seepage and outflow, the lake's water level and total water amount can rise. Thus the reasoning is: rainfall → surface runoff and inflow → more water in the lake. Option A is wrong because water does not only decrease after rainfall; rainfall commonly increases it, although the final level depends on many conditions. Option B is wrong because rainfall does not make every lake empty; it usually supplies water. Option C is correct because added rainwater can increase the lake's volume. Option D is wrong because water does not turn into salt merely because rain falls; saltiness depends on dissolved minerals, evaporation and water exchange. A careful exam cue is “rain generally raises lake level,” while remembering that the word “can” allows natural variation.