Select all that apply Which of the following are examples of combining summary transitions and preview transitions? Multiple select question. Now that we have reviewed the feasibility of high-speed rail travel in the United States, we can now consider its advantages. As we've seen, high-speed rail in the United States is a feasible technology. Now we should examine whether we can afford it. I will next discuss the advantages of high-speed rail. To implement high-speed rail in the United States, we must overcome economic and social obstacles