Oil is an important ______ material which can be processed into many different products i

The lowest ring of a piston is _____.A.a coil springB.a sealing ringC.an oil distributor r

He thinks he is superior ______ his classmates because his father is an important person.A

Oil is an important ______ material which can be processed into many different products, i

When centrifuging heavy fuel oil, an important factor to consider is the _____（1) flow rat

The capital city of Canada is______, which is an important financial and commercial center

According to the news item, Abyei is______.A．an oil-rich regionB．a part of South KordofanC