We have to find the adequate unit rate for the amount of rainfall over time.
Rainfall amount is expressed as the qoutient of a unit of height and a unit of time.
From the options, all unit rates correspond to "height over time", so they are theoretically correct.
The way to choose the most appropiate is the relation between both quantities.
For example, "meters per second" is a way too high unit for the height (which is usually inches or milimeters, instead of meters) and way too low for the time unit (which is usually per day, not seconds). This unit would have a really small number for any rain.
The most common unit is "milimiters per day", but it is not listed in the options.
Then, we should find a unit rate with a small unit for height and a large unit for time.
From the options, the ony one that has a large unit for time is "centimeters per day", so this is the most appropiate.
If we have to use imperial units, an appropiate unit can be "inches per hour".
For example, a moderate rain is about 7 mm per day. This will be equal to 0.7 cm per day, or:
![7\frac{\operatorname{mm}}{\text{day}}\cdot(\frac{1in}{25.4\operatorname{mm}})\cdot(\frac{1\text{day}}{24\text{hour}})=(7)/(25.4\cdot24)\frac{in}{\text{hour}}\approx0.011\frac{in}{\text{hour}}]()
Answer: the most appropiate is "centimeters per day". It can also be, using imperial units, "inches per hour".