— Shall Brown come and play computer games?
— No, ________ he has finished his homework.
A:when
B:if
C:unless
D:once
一元二次方程x2﹣4x+3=0的两个根分别是⊙O1和⊙O2的半径长,圆心距O1O2=4,则⊙O1和⊙O2的位置关系( )
下列海陆变化中,哪一项是由填海造陆引起的?( )
用下列词语造句
①炫耀
②魁梧