. The teacher advised me to be a doctor, but ____.
21._____by a desire to learn, he was not interested in children’s play and adventure when he was young.
20. The flu is believed________by viruses.
19. They________a lot of suggestions for improving the workers’ living conditions.
18. After having gone____-far, I didn’t want to turn back.
17. One of the mottos for the park makes_____clear that science and business can and must work together to build the future.