Silk ______ one of the primary goods traded along the Silk Road by about 100BC.( )
had become
was becoming
has become
is becoming
Sofia looked around at all the faces: she had the impression that she _____ most of the guests before.
James has just arrived, but I didn’t know he _______ until yesterday.
During his stay in Xi’an, Jerry tried almost all the local foods his friends ________,
Bob called to tell his mother that he couldn’t enter the house, for he ________ his key at school.
Because the shop _________, all the T-shirts are sold at half price in it.