Which of the following is least?

A. 0.105

B. 0.501

C. 0.015

D. 0.15

and how you got it with explaination

In order from least to greatest, it's listed as:

0.015, 0.105, 0.15, 0.501.

0.015 is the lowest number because it is the farthest from being a whole. It starts with. 0, whereas the rest of them have a number higher than 0 after the period.