Final answer:
Milli is the prefix that represents the smallest value amongst the given options, signifying one thousandth, or 0.001.
Step-by-step explanation:
The prefix that represents the smallest value among centi, deca, deci, and milli is milli. Milli signifies one thousandth (1/1,000 or 0.001). For example, there are 1,000 millimeters in one meter. In contrast, centi stands for one hundredth (1/100 or 0.01), deci stands for one tenth (1/10 or 0.1), and deca stands for ten times (10x or 10). Therefore, milli represents a smaller fraction than centi, deci, and deca, making it the smallest metric prefix value among the options given.