Constant correction by a teacher is often counterproductive, as the student may become afraid to speak at all.
Giải chi tiết:
Đáp án là D. counterproductive : không hiệu quả >< effective: hiệu quả
Nghĩa các từ còn lại: desolate: bị tàn phá; unproductive: không phát sinh; barren: cằn cỗi
Biogas can be utilized for electricity production, cooking, space heating, water heating and process heating.
Around 150 B.C. the Greek astronomer Hipparchus developed a system to classify stars according to brightness.