________has recently been done to provide more English books for the students, a shortage of reading materials remains a serious problem.
—Alice promised me to come round to keep you company today. —But she ________. I've been alone all day.
It is impossible to cooperate with a person ________ methods are completely opposed to your own.
Butterflies ________ a sweet liquid produced by flowers, which bees and other insects collect.
The girl in the photo was smiling sweetly, ________.
Electronic products are ________ must for new generation of ________ college students.