Answer:
C) observing
Explanation:
Although the passage is not included in this example, we can still try to figure out what the meaning of the word "ascertain" most likely is. The word "ascertain" means to make sure of something. It also refers to trying to find something out for certain. If we want to engage in either one of this actions, then it is likely that we need to observe what we are evaluating carefully in order to really make sure that our conclusions are right.
