In the following paragraph, which sentence is irrelevant to the topic sentence? "1) Adventure travel is the hot trend in the tourism industry. 2) Ordinary people are no longer content to spend their two weeks away from the office resting on a sunny beach in Hawaii. 3) More and more often, they are choosing to spend their vacations rafting down wild rivers, hiking through steamy rain forests, climbing the world’s highest mountains, or traversing slippery glaciers. 4) People of all ages are choosing educational study tours for their vacations."
A、1.
B、2.
C、3.
D、4.