The two researchers originally set out to study the zebras in Africa and discovered a new species of tiger ______.
| A．by chance | B．in addition |
| C．by nature | D．in need |
We are living in ______ world of developing, ______ world where any problem can be solved in a peaceful way.
| A．the; a | B．a; the | C．the; the | D．a; a |
valley
| A．vocabulary | B． attraction | C．many | D．cave |
loose
| A．shoot | B．outdoors | C．football | D．wool |
accent
| A．official | B．recover | C．recognize | D．pace |
exactly
| A． expression | B． example | C． exhibition | D． exchange |