21. The research group were determined to ___ the experiment until they could ___ a conclusion.
A. carry on; come to B. carry out; arrive at C. carry away; draw D. carry to; reach
22. ---Oh, doctor, The wound on my leg is infected.
---You really shouldn’t have left it _______ to the sun.
A. discovered B. exposed C. opened D. buried
23. ---Who do you suspect _______ having stolen the wallet? ---Hard to say.
A. with B. for C. of D. about
