Which of the following units is the smallest measurement of weight?

The microgram is indeed the smallest unit of weight among the options provided. To understand this, it's helpful to look at the hierarchy of weight measurements in the metric system.

A microgram is one-millionth of a gram (0.000001 grams), whereas a milligram is one-thousandth of a gram (0.001 grams). A gram is the base unit of weight in the metric system, and a kilogram is equal to 1,000 grams. This clearly shows that as you move from micrograms to kilograms, the values increase in size.

By understanding these relationships, one can see that the microgram is the smallest unit on the list, making it the correct answer.