用所给词的适当形式填空

41. It's  ▲  (正常的）to feel nervous on your first interview.

42. --What do you think of our first suspect, Wang Gang?

   ---He seems to be a nice man. I don't think he's    ▲   （有罪）.

43. I don't think Xie Yiming is    ▲   （参与）in this kidnapping.

44. The thief ran very fast and    ▲    （消失）in the dark at once.

45. Three    ▲   (四分之一) of  the surface of the earth is covered with water.

46. I went to the shop to buy a newspaper, but they had  been  ▲   ( 出售 ) out.

47. Everybody should  ▲   (积极)join in this charity to raise money for the poor.

48. --- Woo! You've got so many skirts.

   --- But   ▲   of them is in fashion now.

49. -- You look worried, Daniel. What's the matter?

   ---I have a problem and I don't know how to    ▲    with it.

50. Why don’t you do it by yourself ?

   Well, I don’t think I’m    ▲    to . I need help.