21.Our ______ problem was lack of time to review the details of our plan.
A. principal		B. bare 				C. hardly				D. identical
22.He carefully _________ the key in the lock and opened the door.
A. proceeded		B. endured 			C. provoked			D. inserted
23. My father’s words will always strongly____ my mind.
  A. be impressed upon	B. impress upon	C. impress			D. be impressed in
24. Hi, don’t snap ____ me, I have done nothing wrong.
 A. x					B. at				C. to					D. on
25. Right now, some students do part-time jobs, like____ flyers on the street for some companies. 
 A. passing on			B. passing out		C. passing by			D. passing away