问题描述：
| For our middle school students, some courses are compulsory, while others are ______. |
| [ ] |
| A. flexible B. optional C. impressive D. significant |
考点提示：形容词
最佳答案： | B |
For our middle school students, some courses are compulsory, while others are ______. [ ]A. flexible
For our middle school students, some courses are compulsory, while others are ______. [ ]A. flexible
最佳答案： 