Answer: A. drought
Step-by-step explanation:
A drought is a natural hazard which occurs in a region which receives very low annual rainfall. Due to this reason the area experience desert like conditions for example hot and dry climate, loose or compact soil, and drying up of water resources. The region will experience scarcity of water.
According to the given situation, the amount of annual rainfall received by Boston was reducing according to the data. Therefore, the Boston was experiencing drought.