题目

下列各式中，不是同类项的是（ ） A . 2ab2与－3b2a B . 2πx2与x2 C . － m2n2与5n2m2 D . － 与6yz2 答案：D People are advised to lay particular ____ the need of a balanced diet and proper exercise. A. stress onB. importance of C. stress toD. attempt at