Final answer:
Option A is an example of an hourglass sentence structure.
Step-by-step explanation:
Option A, “Banning plastic bags, the activists say, will redirect funds to infrastructure and spur entrepreneurial efforts to come up with alternatives to plastic,” is an example of an hourglass. An hourglass is a sentence structure that begins with a dependent clause, followed by a free-standing independent clause, and ends with another dependent clause. In this excerpt, the opening dependent clause “Banning plastic bags” sets up the main idea, the independent clause “the activists say, will redirect funds to infrastructure and spur entrepreneurial efforts to come up with alternatives to plastic,” and the closing dependent clause “is an example of an hourglass.”