When you are in China, you can stand ______ to people.
A:close
B:closed
C:open
D:opened
为了探究“滑动摩擦力大小与什么因素有关”,小明设计了如图1所示的实验.
can't的完全形式是 . ( )
继去年上海自贸区挂牌成立后,今年我国又批准建立的三个自贸区是( )