我的看法和两位老师不同,问题句如果使用 appear 也是对的。对于 appear 的这种用法,现代英语中,很多人采用的方法是如果句子是单一相同对比项,对比项是复数,分句动词就用复数,而且分句对比项通常省略,反之,就动词用单数。也有人不使用这种方法,即使单一对比项为复数,分句动词仍然用单数,问题句就是一个例子。difficulties 为复数对比项,但than后动词用单数。当然如果用复数也对。
曹老师的例句:More people came to the party than (had been) invited. (出自《剑桥语法》)这里属于单一相同比较项people,从句省略的也是people,这种情况,虽然两个people数量不同,但分句people 包含在主句主语的people中,分句同类项要省略,避免逻辑上出现重叠。如果说受邀人来的比不受邀的人多,分句比较项一般不省略。More invited guests came to the party than those uninvited. 因为这属于不相同对比项,没有包含关系。
Alex 119老师提供的例句2,属于不同对比项,一个是person, 一个是they, 这时they不能省略。这种情形下,一般分句动词随对比项的单复数而变化。如: The person is less honest or moral than they appear to be. (复数)Alex119 老师的其他例句,我认为分句对比项省略也是对的。作者仅是选择了没省略而已。
另外,不是所有动词都可以这样用,《剑桥语法》曾列出了几十个包括appear在内的可以这样用的动词,但仅是常见的一部分,不是全部。
以上是我个人的理解,不一定对, 欢迎大家指正。我再补充几个外刊例句供比较参考。
appear 用单数:
1. The use of the land to provide "fuel" for horses or oxen also suggests that the contrast between the two countries may be greater than appears in the table.
2.The division between ellipticals and spirals is probably much less sharp than appears at first sight.
3.Deconstruction and empiricism, in fact, are closer to each other than appears on the surface.
appear 用复数:
1. The question of pegging to gold rather than dollars has two deeper implications for the system than appear at first sight.
2.They also average more populist attributes than appear on websites of small townships.
3. It is my impression that Yugoslav relations with the Soviet Union are actually much worse than appear on the surface.