It is fashionable to drive a car, but to drive a car is not nearly as difficult as it is imagined on condition that you ________ the specialized rules.

Living in the central American desert has itsproblems, ________ obtaining water is not the least .

What did you say? –So you _____________ to me

This is ______ English lesson. I hope you will enjoy English.

________, the Internet was only used by the government.But now it’s widely used in every field.