There are so many foggy days these days. We all wonder .
A. how is the air polluted
B. why the air is polluted seriously
C. what are the real reasons
Scientists say they are beginning to _____ in the fight against cancer.
| A．break in | B．break out | C．break down | D．break through |
As the spring comes, the flowers began to _____.
| A．come out | B．come in | C．come on | D．come down |
As we all know(众所周知), the dinosaur has _____.
| A．died | B．died out | C．died from | D．died of |
The kids are looking forward to ______ Spring Festival.
| A．celebrate | B．to celebrate | C．celebrating | D．being celebrated |
Everyone in the class studied very hard since no one wanted to _____.
A. fall down B fall off C. fall behind D. fall out