Using the verb 'use' correctly

Good day!

Got some questions on the top of my head.

1.) A.) It is used to make concrete and brick.
B.) It is use to make concrete and brick.

2.) A.) He used to be my hero.
B.) He use to be my hero.

3.) A.) What it is used for
B.) What it is use for

Please tell me which (and why) of the sentences or phrases in nos. 1-3 are correct.


TOEIC short conversations: Clarifying information on an invoice[YSaerTTEW443543]