题目

以下不属于酯类物质的是（ ） A . 甘氨酸 B . 硝化甘油 C . 脂肪 D . 硝酸纤维 答案：A---How was their last weekend? ---Great. They had a picnic in the park and enjoyed _______.A．themB．theyC．theirD．themselves