下列说法可充分说明P(g)+Q(g)  S(g)+R(g)在恒温、恒容密闭容器中的反应已达平衡的是 [ ]

A．容器里P、Q、R、S四种物质共存

B．容器里Q、R的体积分数不再改变

C．容器内气体压强、密度不随时间变化

D．单位时间内同时生成n mol P和n mol S

—He thinks that girls are smarter than boys when it comes to learning English.

—But two years ago he thought_______.

A．so

B．otherwise

C．opposite

D．different