If y is a number less than 0 but greater than -1, which of the following expressions has the greatest value?

a 100y
b y^2
c y^3
d y^4
e y^5

-1 < y < 0. y is negative.

Any positive power of y > 1 will make it larger because y is negative. The higher the power, the greater the value.

Therefore, y^5 has the greatest value.