简单问题,马上给分,is和does用法

1.这种情况下，先把它变成陈述句，即：the company sells XXX
这里面谓语是sell，如果变成疑问句的话，就需要助动词，由于是第三人称单数，那就只能用does；
What is Lucy calling about? 这句变成陈述句是：Lucy is calling about XXX.

这个里面，谓语是is calling，用的是现在进行时，有be动词，那变成疑问句就不用另加助动词了，就用is。

2.这句是一般疑问句，直接变成陈述句是：Lucy knows Lily. 因为主语Lucy是第三人称单数，所以谓语动词know要加s。变成疑问句的时候，要加助动词do，由于是第三人称单数，则用does， Does Lucy know Lily?
如果你用is，那还原成陈述句就变成了Lucy is know Lily, 明显是错误的。

what do the company sell?
They want to know what KIND THING they sell, not past, right now, or future.

what is Lucy calling about?
question is RIGHT NOW lucy call for wtaht, so "be v+ing" correct.

Does Lucy know Lily?
If you ask somebody who knows something or not. You have to use "DO"
"is" make no sence

你试试反过来看看，

The company sell books.
What do the company sell?

The company is selling children book now at 50% off.
What is the company selling now at 50% off.

这里有一点要补充一下， “The Company” 可以是单数，也可以是双数
所以也可以是
The company sells books.
What does the company sell?

The company are selling children book now at 50% off.
What are the company selling now at 50% off.

Does Lucy know Lily?
(为什么用does,不用is,露西知道不知道李莉,应该用is吧??)

Lucy knows lily.
Does Lucy know lily?

所以在问题用 Does， 不用 is

陈述句：The company sells ***.
问句：What does the company sell? (因为 sells = does sell)

陈述句：Lucy is calling about ***.
问句：What is Lucy calling about? (这是简单的倒装问句）

陈述句：Lucy knows Lily.
问句：Does Lucy know Lily? (因为 knows = does know)