Silk ______ one of the primary goods traded along the Silk Road by about 100 BC.
A:had become
B:was becoming
C:has become
D:is becoming
—Would you like to go and see a film?
—Sure, the TV programmes are too _______.
如图所示的现象中,属于光的色散现象的是( )
(2x﹣1)(3﹣2x)5的展开式中,含x次数最高的项的系数是____ (用数字作答).