流脑高发年龄().
A.<6个月
B.6个月~2岁
C.3~5岁
D.6~10岁
E.11~15岁
参考答案:B
___________ I toured Zhangjiajie, I was deeply impressed with its beautiful scenery.
A.For the first time
B.At first
C.It was the first time
D.The first time
已知正六棱锥底面的边长为2cm,侧棱长为4cm,求正六棱锥的体积。