Flash mobs seem both interesting and safe. Participants are irresponsible.

Which of the following correctly combines these two sentences into a complex sentence?

A.
Flash mobs seem both interesting and safe, unless participants are irresponsible.
B.
Flash mobs seem both interesting and safe, but participants are irresponsible.
C.
Flash mobs seem both interesting and safe, yet participants are irresponsible.
D.
Flash mobs seem both interesting and safe, participants are irresponsible.

Please select the best answer from the choices provided

A
B
C
D