1) The students enjoyed their history classes.
Who enjoyed their history classes? ***
Which classes did the students enjoy?
2) Most of the staff like the new president of the company.
Who likes the new president of the company ? (subject)
Who do most of the staff like? (object)
3) Simon has lost his ID card.
What has Simon lost?
Who has lost his ID card?
*** Who enjoyed HIS history classes? = такой вариант тоже правильный )))
1) Who enjoyed their history classes?
Which classes did the students enjoy?
2) Who likes the new president of the company? (subject)
Who do most of the staff like? (object)
3) What has Simon lost?
Who has lost his ID card?