Looking at the curve we can clearly see that Y is going to be growing. The reason Y is the slowest is that Y has the least amount of interest per annum, and X is going to be the second slowest because it has a larger interest. W is the fastest growing one in that while the amount of interest is the same as X, W earns interest more frequently and as such grows the fastest.
Coming to think of it it's like asking how frequently do you water your plants. The more frequent you do it the more they grow. Where watering is the money earning interest and plants are like money.