The main reasons why architects use toughened glass is because it is slightly cheaper than other kinds of glass.

A．the Duchess of Windsor is regarded as a woman of virtue
B．looking slim is a symbol of having a large fortune
C．being thin is viewed as a much desired quality
D．religious people are not necessarily virtuous

A．were closely related to their religious beliefs
B．changed from time to time
C．varied between the poor and the rich
D．led to different moral standards