The price of beer （） from 50 cents to $ 4 per liter during the summer season.

单项选择题He came back late,（） which time all the guests had already left.

A．after
B．by
C．at
D．during

单项选择题The author used the example of a rattle to show that （）.

A．in toy-making there is a continuity in the use of materials
B．even the simplest toys can reflect the progress of technology
C．it often takes a long time to introduce new technology into toy-making
D．even a simple toy can mirror the artistic tastes of the time