The phrase "in relation to" in the third sentence of the first paragraph can be replaced by _____________.

A．may result from their frequent use of teeth equipment
B．is that all their teeth are strongly rooted
C．can not be reflected in their cultural activities
D．has something to do with their eyes

A．There has been ups and downs in the development history of plastic technology.
B．Nowadays plastics help people to live a more convenient life in modern world.
C．Since plastic technology does not have a long history, there are no plastic antiques at all.
D．Collecting cheap but beautiful plastic antiques can be fun sometimes.