______ the average age of the population increases, there are more and more old people to care for.
| A． |
Unless |
B． |
Until |
C． |
As |
D． |
While |
All we need a small piece of land where we can plant various kinds of fruit trees throughout the growing seasons of the year.
| A．are | B．was | C．is | D．were |
Generally, students’ inner motivation with high expectations from others ______ essential to their development.
| A．is | B．are | C．was | D．were |
The university estimates that living expenses for international students ________ around $8,450 a year. which ________ a burden for some of them.
| A．are；is | B．are；are |
| C．is；are | D．is；is |
His teacher told him that since his parents were working abroad, either his grandparents or one of his uncles ______ allowed to come to the parents’ meeting .
| A．was | B．were |
| C．are | D．is |
English is a language shared by several diverse cultures, _________ uses it differently.
| A．all of which | B．each of which |
| C．all of them | D．each of them |