A:his not being able to come
B:his being not able to come
C:his being able not to come
D:him not being able to come
如图表示配制一定物质的量浓度的NaCl溶液的部分操作示意图,其中有错误的是( )
如图所示,在使用各种工具的过程中属于费力杠杆的是 ( )
执行如图所示的程序框图,输出S的值为12时,k是( )