The words given above are<em> </em><em>prepositions</em> - words which indicate the relationship between a noun/pronoun and other words within a sentence. Common prepositions used in the English language are<em> at, by, beside, above, at, before, near, on, to, under, upon, </em>etc. For instance, preposition <em>'by' </em>is often used to identify the agent that performs the action of the verb. In this case, it is stated that the questions are asked "<em>by</em>the doctor's assistant."