中颅窝脑膜瘤是()。
A.球形肿瘤
B.脑内肿瘤
C.良性肿瘤
D.恶性肿瘤
E.脑外肿瘤
参考答案:E
He asked them to come to his office one _____.
A.at a time
B.at all time
C.at times
D.at one time
浮选法在工业上应用至今已有()多年历史。
A.一千
B.二千
C.一百
D.三百