As far as some people are concerned, dietary habits may be one of the reasons for SAD.

A．To teach students how to use English.
B．To provide language learning opportunities.
C．To offer job positions for graduating students.
D．To help students prepare to enter institutions of higher learning.

A．The importance of good manners.
B．The art of saying thank you.
C．The secret of staying pretty.
D．The difference between elegance and good manners.