He has ________ in touch with his foreign friends for many years.
A:kept
B:had
C:keep
D:have
已知α,β是两个不同的平面,m,n是两条不同的直线,给出了下列命题:
①若m⊥α,m⊂β,则α⊥β;
②若m⊥n,m⊥α,则n∥α;
③若m∥α,α⊥β,则m⊥β,
④若α∩β=m,n∥m,且n⊄α,n⊄β,则n∥α,n∥β( )
0.05.9. ____ 0.0.59.
1.6÷0.13____1.6
7.3×0.99____7.3×1.01
5.67÷0.12____56.7÷1.2.