—Have you finished your book report?—Not yet. I couldn't________on it with so loud music next door last night.
The first few years in the 21st century ______ the rapid rise of China as a world economic power.
Visitors to the National Museum can avoid long lines at the ticket booths by purchasing tickets ____.
She told me that she would not go with us if it ____ the next day.
I know one of the things I was unsure about was _____ hard it would be to climb this mountain.
Some researchers are finding that daydreaming may be important to ______ mental health and it is ______ good means of relaxation.