$1.$ The paintings that haven't been found yet, were stolen from the museum.

$2.$ Ba and Lan go to school on foot.

- go on foot = walk (v.): đi bộ.

$3.$ You can choose more than twenty movie theaters in the city.

- S + can + V (bare).

$4.$ She asked me what I was going to do after I graduate from school.

- Câu hỏi tường thuật: S + asked + O + wh- words + S + V...

$5.$ The Statue of Liberty was presented to the United States by France in 1876.

- Câu bị động thì quá khứ đơn: S + was/ were + V (Pii) + (by O).

$6.$ Honda is famous for making a lot of cars. (Câu này mình không rõ).