A．The lower-income people are very sensitive to cold bacteria．
B．The lower-income people have lower resistance．
C．The crowded space and poor diet make the lower-income group easy to be infected．
D．The bad mood of the lower-income group makes them very easy to be infected．
A．It is recalled after a long time．
B．It is studied at all levels．
C．It is repeated again and again．
D．It is processed in the mind．
A．Represent their levels of ability in English．
B．Listen to a recording of a paragraph in English．
C．Circle the words they heard in the paragraph．
D．Take a language proficiency test of the paragraph．