800 câu trắc nghiệm Điền từ Tiếng Anh có đáp án - Phần 20

They made working there fun even when we had to deal with customers (4)______ got on our nerves.

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They made working there fun even when we had to deal with customers (4)______ got on our nerves.

which

why

when

who

Giải thích

D là đáp án đúng