Đáp án A
– that people use – phía sau là một động từ => đằng trước là mệnh đề quan hệ để bổ sung nghĩa.
In this way, we can put you in a (59)_________ at the most suitable level.
Scientists are unsure of the reason for this (70)_______ on the global scale either.
The trains which go through the Chunnel can travel at up to 300km/h due to the(31)_________ electrical system.