1. 完形填空

    A marine biologist placed a shark into a large holding tank and then released several small bait fish into the tank. The result met your 1, the shark quickly swam across the tank, attacked and ate the smaller fish.

    The biologist then 2a strong piece of fiberglass into the tank, creating two 3parts. She then put the shark on one side of the 4fiberglass and a new set of bait fish on the other. 5, the shark quickly attacked. But this time, the shark 6because it knocked hard against the fiberglass 7. Determined, the shark kept 8this behavior every few minutes, but 9. Meanwhile, the bait fish swam around 10in the second part. Eventually, the shark 11hope of hunting. This experiment was carried out several times. Each time, the shark got less 12and made fewer attempts to attack the fish, until it 13hitting the fiberglass and simply stopped attacking. The biologist then 14the fiberglass, but the shark didn't attack. The shark was trained to believe a 15existed between it and the bait fish, 16the bait fish could swim wherever they wished, free from harm.

    Many of us, after experiencing setbacks and failures, 17give up and stop trying. Like the shark in the story, we believe that 18we were unsuccessful in the past, we will always be unsuccessful. 19, even when no "real" obstacle exists between where we are and where we want to go, we 20see obstacles in our heads.