英文問題 be的問題

你好，首先我想说我们发问的时候应该是没有 How XXX can be XXX 的结构。

通常我们发问的结构都会像以下的那样，

1) auxiliary verb + subject + main verb + complement of the sentence
- Do you want dinner? (Do + you + want + dinner)
- Can you drive? (Can + you + drive)

2) question word + auxiliary verb + subject + main verb + complement of the sentence
- When will we have lunch? (When + will + we + have + lunch)
- Where do you live? (Where + do + you + live)

3) 有时我们也会写到类似这样的结构。。。 How much weight can this plastic box carry?

所以，我会给个类似你想问的结构。。。
- How can you be so sure? (你怎么这么有把握)

你又是否知道 sure 在这里是什么吗？它其实是个形容词 (adjective) 来的。

除此之外，你也说对了，我们是可以在 can be 的后面用名词 (noun) 的。
例如，How can I be a model / a millionaire / a teacher?

但如果你想在 can be 的后面用动词 (verb) 并且用 past participle (verb + -ed) 的话，那就会把那句子变成了被动式 (passive voice) 了。
例如，How can these unusable papers be recycled? (怎样能把这些废纸或报纸被再循环或利用?)

不过，请你留意的是不一定每个动词后面加了个 -ed 就会把它用作被动式的，某些动词后面加了个 -ed 就会变成形容词了。
譬如，
1) excite (verb) ---> excited (adjective)
2) interest (verb) ---> interested (adjective)
3) bore (verb) ---> bored (adjective)

也想说 can be 的后面是没有用原本的动词的。

希望能帮到你咯。。。: )

BE can change to as follows:
is, am, are, was, were, been.
i.e. Mary have been six years old since 2008.
i.e. I have been to Macau several times.
i.e. You should be changed the hair colour before you come to school.
希望你會明白＆幫到你啦！！

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How can it be?
How can it happen?
How can we do this to Tom, who has been so kind to us?
How can we be so cruel to Tom, who has been so nice to us?
be + adjective not verb.