An experiment that is most appropriate to prove the hypothesis that it rains more in the month of april than in the month of march would be
1. count how many days it rains in april
2. measure the growth of flowers during the month of march
3. count the number of sunny days in march and april
4. collect and measure the amount of rain in march and in april

4. Collect and measure the amount of rain in March and in April

Explanation - Rainfall can be measured by instruments like rain gauge. But in case rain gauge is not available then the rain water can be collected in a vessel having funnel at the top.

Measuring the amount of water falling each day in the month of march and april would give the idea about which month has more rainfall. The measurement might not be accurate but it gives a brief idea about how much centimeter of rain is occurring in both the months.