My mother is busy________the room. [ ]
A. clean
B. to clean
C. cleaning
D. cleans
答案:C
将Rt△ABC沿直角的角平分线CD折成直二面角(平面ACD⊥平面BCD),则∠ACB的度数是( )
A.90°
B.60°
C.45°
D.由直角边的长短决定
为视图重命名的命令是
A.MODIFY VIEW
B.CREATE VIEW
C.DELETE VIEW
D.RENAME VIEW