The correct answer is C. week is.
The reason why this is incorrect is because there has to be a comma between the words week and is. The clause 'who is visiting the US this week' is an appositive clause, which means that it has to be set off from the rest of the sentence using commas. Hope this helps!
4) a question with more than one answer! :D
The answer is A. (Boring classes are just as important as interesting ones.)
C uses the most positive form of an adverb
