Answer
See below.
Work Step by Step
We know that $probability=\frac{\text{number of favourable outcomes}}{\text{number of all outcomes}}$
a) An event of a flood from the other years thus the probability is the probability of a flood raised to the power of $2$, which is: $0.2^2=0.04$
b) An event of a flood from the other years thus the probability is the probability of a flood raised to the power of $3$, which is: $0.2^3=0.008$
c) An event of a flood from the other years thus the probability is the probability of having no flood raised to the power of $4$, which is: $(1-0.2)^4=0.8^4=0.4096$
