Here's an attachment with the answer key to all of your questions.
According to the Scientific Method, in order to make a controlled experiment you NEED to have an hypothesis.
A controlled experiment consists of a test done by a scientist in which only one or a few variables are changed while the others remain constant in order to prove or disprove a hypothesis. This hypothesis is key to said experiment because it provides the starting point from which the professional can begin the procedure, as it helps focus on the subject that one is trying to get results from. Without a clear hypothesis, the outcome of the experimentation will not be valid nor specific.
The correct answer is C. The dog buried a bone under our porch.
The prepositional phrase is, under our porch.
The first one "I'm confused," Jim said, "is it safe? Or not?"
