Need help with these simple daily grammar?

[rozinac]

Which one of these sentences is correct?

1.
a. Has the mailman come?
b. Has the mailman came?

2.
a. I did not know.
b. I did not knew.

[Temico]

Which one of these sentences is correct?

1.
a. Has the mailman come?
b. Has the mailman came?

2.
a. I did not know.
b. I did not knew.

1a.The verb in the sentence is "has come" which is correct.
1b.The verb "has came" is incorrect because there is no such verb in English.

2a. The verb in the sentence is "did know" which is correct.
2b. The verb "did knew" is incorrect because there is no such verb in English.

[MrPedantic]

Which one of these sentences is correct?

1.
a. Has the mailman come?
b. Has the mailman came?

2.
a. I did not know.
b. I did not knew.

To supplement Temico's answer:

With the present perfect, you use the present tense of "to have" + the past participle, e.g.

1. I have broken the window.

With the auxiliary "to do", you use the appropriate form of "to do" + the bare infinitive, e.g.

2. I didn't break the window.

In 1b and 2b, you've used "do/have" + the simple past form of the verb. This combination isn't correct.

MrP