若抛物线y=x2-4x+c的顶点在x轴上,则c的值是( )。
4
—What would you like for breakfast?
—I'd like a glass of milk and some bread, but I ______ porridge and eggs. [ ]
A. dislike
B. disagree
C. discover
D. discuss
可作为栓剂制备用基质的是()
A.聚乙二醇
B.液状石蜡
C.凡士林
D.甘油
E.羊毛脂