-4的绝对值是
A.2
B.4
C.-4
D.16
答案:B
题目分析:-4的绝对值=
点评:本题考查绝对值,要求考生掌握绝对值的概念,会求任何数的绝对值,属基础题
He asked us to _______ him _______ carrying through their plan. [ ]
A. assist; with
B. help; to
C. help; with
D. assist; in
pH梯度萃取法适合分离()
A.生物碱
B.黄酮苷
C.游离蒽醌
D.黄酮苷元
E.挥发油