属于简易判断润滑油变质的方法是（）
A、红外光谱分析
B、铁谱分析
C、滤纸斑点试验法
D、化验分析
参考答案：C
Scientists think that the continents ____ always where they ___today.
A．aren't; are
B．aren't; were
C．weren't; are
D．weren't; were
—How many practical plans has your deskmate made this week?
— . All have turned out disappointing.
A．None
B．Nothing
C．Nobody
D．No
