According to the text, the word" regression" in ( Line 1, Para. 4) means ______.

A．culture shock is an occupational disease
B．culture shock is caused by the anxiety of living in a strange culture
C．culture shock has peculiar signs
D．it is very hard to cope with life in a new setting

A．like all other diseases it has its own signs and cure
B．only those who engage in culture work suffer from it
C．it is hard to get rid of
D．only those living in a strange culture may experience it