钻床空运转试验中主运动在（）转速时，运转时间不得低于0.5小时，主轴轴承温度不得超过70℃。
参考答案：最高
___ staying at hotels in Red River Village, tourists can help the villagers make money so that they
can take _____the river and the birds. [ ]
A. By; care for
B. By; care of
C. Through; care about
D. With; care of
正常角膜地形图可表现为（）
A.领结形
B.椭圆形
C.不规则形
D.圆形
E.以上均是
