17000 bài tập tách từ đề thi thử môn Tiếng Anh có đáp án (Phần 3)

By 1820, there were over sixty steamboats on the Mississippi river, were quite luxurious.

371/1620

By 1820, there were over sixty steamboats on the Mississippi river, _________ were quite luxurious.

which many

many of them

many of which

many that

Giải thích

Chọn B