4. turn to:转向,求助 e.g. He turned to the study of medicine He often turns to the teacher for help 5beof+抽象名词=be+ad e.g. The work is of great importance. The work is very important.4. turn to: 转向，求助 5. be of+抽象名词 = be + adj. e.g. He turned to the study of medicine. He often turns to the teacher for help. e.g. The work is of great importance. = The work is very important