In manufacturing, cheaper materials are constantly being for the better, more expensive kind.
| A．maintained | B．cancelled | C．substituted | D．deposited |
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They appearedme, so I had to explain to them.
| A．misunderstanding | B．misunderstood |
| C．to be misunderstood | D．to have misunderstood |
If China’s space technology has achievedbreakthrough in this field, it really is
amazing wonder.
| A．the; an | B．a; an | C．不填; the | D．a; 不填 |
Though he is in his late sixties, the well-known biolo
gist begins each day ____ a sense of adventure and a sense of curiosity.
| A．in | B．with | C．of | D．at |
The chairman was about to declare the conference open ____ the lights went all out.
| A．as | B．while | C．then | D．when |
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