expert

Expert means someone who knows a lot about a specific area of knowledge.

Expert can be used as a noun or an adjective. In this exercise, expert is used as a noun.

For example:

Professor Jacobs is a well-known expert on using the internet to teach English. All the other teachers go to him for advice.

I can answer any simple questions that you have, but you will need to go to an expert to answer the more difficult questions.