【C6】A．indoorB．outdoorC．fleaD．mass

What distinguishes the end－Permian mass extinction from other similar devastations？A．Chang

What standard introduced by Ford in 1913 is considered advanced even today？A．Mass producti

【C3】A．a number ofB．a great many ofC．a sum ofD．a mass of

Which of the following is a derived word（派生词)？A．undercookB．downfallC．mass-produceD．stea

A．indoorB．insideC．outdoorD．outside

Beijing is a good place to study mass media since