One of the most important results of research into ageing has been to pinpoint the significance of short-term memory. This faculty is easily (1)_____ as ageing advances. What seems to (2)_____ is that in formation is received by the brain, (3)_____ scans it for meaning in order to decode it at some future time. It looks as if the actual (4)_____ of the short-term memory itself may not change too much (5)_____ age. A young man and a man in his late fifties may (6)_____ be able to remember and repeat a(n) (7)_____ of eight numbers recited to them. But what (8)_____ change is that when the older man is asked to re member anything (9)_____ between the time he is first given the numbers to memorise and the time he is asked to (10)_____ them, he will be much less likely to remember the (11)_____ numbers than the young man. This is because the scanning stage is more easily (12)_____ by other activities in (13)_____ people. In (14)_____ living one experiences this as a fairly minor (15)_____—a telephone number forgotten while one looks (16)_____ an area code, or the first part of (17)_____ street directions confused with the fast because the last "turn lefts" and" turn rights" have interfered (18)_____ remembering the first directions. In more formal learning, however, the (19)_____ of short-term memory is more than just a mild social embarrassment. It can be a serious bar to further (20)_____ or indeed to any progress at all.
【答案解析】解析：本句解释人脑记忆的基本原理。整句结构为：What引导的是主语从句，系动词后面是表语从句"that information is received by the brain…"。可以看出，主语是短期记忆过程中所发生的事情，故"happen"正确。work作不及物动词时，它的含义是"起作用，正常运转"，放在这里不符文意。exist表示某种存在的状态，但文中指的却是一个事物发生的动态过程。do作不及物动词时也没有"发生"的含义。
【答案解析】解析：average意为平均数，放在文中，"an average of eight numbers"谈的是年轻人和老年人平均能记住的八个数字。语意通顺，符合题意。an amount of后接不可数的事物，意为"大量的"，放在这里不合适。而percentage和 proportion都无法与后面的eight numbers搭配。
【正确答案】
C
【答案解析】解析：本题首先考查时态。首先，本文前面一直在用一般现在时，所以这里也应该用一般现在时，而"does"符合要求。其次，本句由but引导，表转折，这与前面"not change too much"相对应。这里用"does change"表示强调。其余选项或为过去时，或为将来时，且都不表示强调。
【正确答案】
A
【答案解析】解析：第一处空白处谈到短期记忆能力"is easily disturbed"，随后又谈到老年人和年轻人记忆的容量本身是相同的，可以看出老年人和年轻人的差别在于对干扰的耐受力不同。而本空白处下文谈到"is more easily…by other activities"，由此可以看出，此处应该指在记忆数字的间隙让他们记忆其他东西，从而形成干扰。故"else"正确。"more"放在这里不合适，因为文中强调的是其他事物的记忆会对原来的记忆造成干扰，而不是强调是否能记更多的事情。particular和special都投有"其他"的含义，不正确。
【正确答案】
D
【答案解析】解析：the time he is asked to…them显然是指将记忆的数字复述出来的时候。四个选项中仅有"repeat"有复述的含义，故D项正确。