students'
This is because in, "We were impressed by several students' drawings," many students are owning many drawings.
student's will not work because this sentence does not say that only one student owns this one drawing. ** **
** students** will not work because this is not possessive.
The correct word to complete the sentence is "students'" because it indicates that several students own multiple drawings. The other options either imply possession by a single student or do not convey possession at all. Thus, we need the plural possessive form to match the structure of the sentence.
;