I think ____ of the materials I listened to at the beginning of the exam ____ easy.

So difficult _____ it to adjust to an English-speaking environment that he determined to learn English hard.

Now more people are paying attention to the school bus safety. — So we believe ________ there will be fewer accidents in the future.

______ is this pen? [ ]

Liu Yang is the first Chinese woman astronaut ______ has ever traveled in space.