请教一道sat真题语法According to some demographers, the number of United S_英语解答

请教一道sat真题语法
According to some demographers, the number of United States citizens aged 65 or older is likely to rise to 87 million by 2050.

请问一下by 2050不是要用完成时吗?为什么是likely to rise而不是have risen?

人气：445 ℃　时间：2020-02-03 17:56:59

解答

be likely to do sth.在可能做某事,
by 2050 表示的是将来时间,如用have risen,岂不是"人数已经上升到...",这显然不合事实.by + 将来一个时间点不是应该用将来完成时的吗如此句中没有likely , 可这样用:the number of United States citizens aged 65 or older will have risento 87 million by 2050 .