Amber is writing a research paper about animal intelligence. Here is her introduction: (1) At one time in history, it was believed that the ability to make tools was what defined the human race. (2) A certain intelligence has been associated with the ability to create and use tools. (3) New research supports that crows not only make tools, but they are also a lot smarter than we may think.

What is the thesis statement in Amber’s introduction?

sentences 1 and 3
sentence 2
sentence 3
sentences 2 and 3