800 câu trắc nghiệm Điền từ Tiếng Anh có đáp án - Phần 16

The development of open learning, (1)_____ it possible to study when it is convenient for the students, has increased the opportunities available (2)_____ many people.

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The development of open learning, (1)_____ it possible to study when it is convenient for the students, has increased the opportunities available (2)_____ many people.

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