. The young ______ the vital forces in our society.
A.is
B.has been
C.are
D.have been
答案:C
一般来说,中国人膳食中n-6脂肪酸的含量高于n-3脂肪酸。( )
如果∠α=n°,而∠α 既有余角,也有补角,那么n的取值范围是[ ]
A.90°<n<180°
B.0°<n<90°
C.n=90°
D.n=180°