增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1）每处错误及其修改均仅限一词；

2）只允许修改10处，多者（从第11处起）不计分。

    In the future, life will be very different for that of today. First, with medical research develop faster and faster, on the average, a person will live to the age of about 120. Second, because of the discover of new energy, environmental pollution will under control. Third, people's daily life will change greatly, either. For example, robots will do all your houseworks for you; your chair will change its color to match which you're wearing; you can also put your mobile phone round your wrist and see the caller after you are speaking; we even can take a new elevator into space for a holiday.

合唱时“低音声部”和“高音声部”中的“低”和“高”是指（   ）