I would say that although (A) and (B) might be used in casual conversation, they are technically not ideal, because "is arriving" is in the present progressive tense, which would be inappropriate for an event "tomorrow." (C) and (D) are slightly better for the first half, although also not ideal (see below). My preference would be for (C), which uses the present progressive tense "are looking." That tense is appropriate because presumably the young people "are looking" forward to his performance right at this moment. (D) is also fine, though the use of the present simple tense implies that it is something that young people look forward to in general, and not necessarily right at this moment.

Of course, if I could add it, I would prefer (E) "Justin Bieber will arrive in New York tomorrow and a lot of young people are looking forward to his performance."

Phoenix, I don't think your teacher is wrong - I think all four of these could be heard in a native English speaker's conversation. The differences, in my opinion, are just subtle shades of meaning. ELIABETH-ANNE, do you have a particular reason for preferring (A) in this case?

Choice A completely.

And I am in NY, please don't tell me that silly boy is coming here !!!!   :-)

Thank you, Adam. My teacher taught me that "be doing" can be used to show the future tense. For example, Justin Bieber is coming tomorrow. So she said A is correct. Is she wrong?