This question is simply a matter of knowing the definition of terms being used in your class. So let's look at the 4 options and see what makes sense.
spectrometry
* This is the determination of elements based upon the light spectrum associated with the elements. It can be either an emission spectrum you get by energizing the substance under test, or an absorption spectrum to see what wavelengths the substance absorbs. But in either case, this doesn't make sense in the statement, so it's a wrong answer.
LD50
* This terms means "Lethal Dose 50%" which is the amount of the substance needed such that half of the creatures that receive that dose die. In the context of the statement, this doesn't make sense, so it's a wrong answer.
pharmacokinetics
* This is the study of how drugs move through the body and are metabolized. This sounds like something that makes sense for the statement in the question, so it's most likely the correct answer. Let's see what the next choice is.
chromatography
* This is a laboratory method of separating substances using differential rates of diffusion. This doesn't make sense given the statement in the question, so it's a wrong choice.
So of the 4 available choices, 3 of them do not make sense given the statement in question and the only one that does make sense is "pharmacokinetics"</span>
