— Can you lend me the book Gone with the Wind?
— Sorry. I returned it to the library just now. Maybe it is still ____.

Whether the buildings in this area should be pulled down has remained ________; people are still looking for other possible solutions.

Can you tell the ________ difference between the words “require” and “request”? I sometimes get puzzled by their meanings.

The research lacks  evidence, and therefore, its conclusions are doubtful.

Several hours later, with the help of the police, the students managed to escape from the dangerous situation, ______.

What ______ me was that there was a ______ look on her face due to the ______ problem.

The secretary arranged a(n)___________time and space for the applicants to have an interview.

Natural disasters occur at ________ times, so it is always difficult to warn people in advance.

Many doctors complain that they don’t have ______ working hours, for they have to wait for patients all day long in the hospital.

While there are some differences in the educational systems in many countries in the world, education itself is ______.