Question 33 : They built the cathedral in the 19th century.
⇒ The cathedral was built in the 19th century.
( Bị động ở thì quá khứ đơn : S + was/were + VPII + by O )
Question 34 : The girl has gone out. Do you know her ?
⇒ Do you know the girl who has just gone out ?
( Mệnh đề quan hệ xác định "the girl" chỉ người → "who" )