Part V Cloze (15 minutes)

　　Directions: There are 20 blanks in the following passage. For each blank there are four choices marked A), B), C) and D) on the right side of the paper. You should choose the ONE that best fits into the passage. Then mark the corresponding letter on Answer Sheet 2 with a single line through the centre.

　　The human nose is an underrated tool. Humans are often thought to be insensitive smellers compared with animals, 62 this is largely because, 63 animals, we stand upright. This means that our noses are 64 to perceiving those smells which float through the air, 65 the majority of smells which stick to surfaces. In fact 66 , we are extremely sensitive to smells, 67 we do not generally realize it. Our noses are capable of 68 human smells even when these are 69 to far below one part in one million.

　　Strangely, some people find that they can smell one type of flower but not another, 70 others are sensitive to the smells of both flowers. This may be because some people do not have the genes necessary to generate 71 smell receptors in the nose. These receptors are the cells which sense smells and send 72 to the brain. However, it has been found that even people insensitive to a certain smell 73 can suddenly become sensitive to it when 74 to it often enough.

　　The explanation for insensitivity to smell seems to be that brain finds it 75 to keep all smell receptors working all the time but can 76 new receptors if necessary. This may 77 explain why we are not usually sensitive to our own smells we simply do not need to be. We are not 78 of the usual smell of our own house but we 79 new smells when we visit someone else's. The brain finds it best to keep smell receptors 80 for unfamiliar and emergency signals 81 the smell of smoke, which might indicate the danger of fire.

　　62. [A]although [B]as [C]but [D]while

　　63. [A]above [B]unlike [C]excluding [D]besides

　　64. [A]limited [B]committed [C]dedicated [D]confined

　　65 [A]catching [B]ignoring [C]missing [D]tracking

　　66. [A]anyway [B]though [C]instead [D]therefore

　　67. [A]even if [B]if only [C]only if [D]as if

　　68. [A]distinguishing [B]discovering [C]determining [D]detecting

　　69. [A]diluted [B]dissolved [C]determining [D]diffused

　　70. [A]when [B]since [C]for [D]whereas

　　71. [A]unusual [B]particular [C]unique [D]typical

　　72. [A]signs [B]stimuli [C]messages [D]impulses

　　73. [A]at first [B]at all [C]at large [D]at times

　　74. [A]subjected [B]left [C]drawn [D]exposed

　　75. [A]ineffective [B]incompetent [C]inefficient [D]insufficient