Which of the following is a complex sentence?

A. As Jake was reading the email from June yet again, the flight attendant coughed gently to get his attention.

B. I would like to visit the Kinshasa, but I understand the city is unsafe for foreigners.

C. I simply cannot make heads or tails of rap lyrics, but I suppose I'm just too old to understand them.

D. Check out the editorial page in today's paper and you'll notice the piece by George Will.

I'm thinking it's A I just want to double check