When the number of measurements increases, what happens to the uncertainty? do not simply say it increases or decreases, there is a specific change and this is what we are looking for here.

The uncertainty decreases

Explanation:

When  multiple measurements are made the size of the sample increases. The uncertainty component caused by the variability of repeated observations (also known as "Type A uncertainty") can be calculated by the equation:

where  

is the uncertainty  

is the standard deviation of the sample and

is the number of samples taken

As a result, when increases the uncertainity decreases

it's all four options.