I believe they are common because people believe that is where we could be headed. Will we run society into the ground, or will we prosper? Will the society be a "Divergent" or "Giver" society or will it exist as it does today? Since we have no way of knowing, we pretend we do.
A sentence that includes an independent clause and at least one dependent clause is called a complex sentence.
The answer is letter D (risks of secondhand smoke)
