命题“存在正实数x,使得lgx≤1”的否定是( )
任意正实数x>0,使得lgx>1
It was ______ great shock to the world that two airplanes crashed into ______ World Trade Centre in New York on Sept. 11.
A.a; /
B.the;the
C.a;the
D./;the
主动脉瓣关闭不全扩张型心肌病
A.主动脉型心
B.二尖瓣型心
C.双侧心界扩大
D.心绝对浊音界扩大
E.心底浊音区扩大