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

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).

is this the question?