矿井变电所的主要变压器不应少于（）台，当一台停止运行时，其余变压器的保证一级和二级负荷用电。
A、2
B、3
C、4
参考答案：A
根据句意填入所缺的单词。
1. August is the _____ month of a year.
2. _____ is the second month of a year.
3. _____ is the first month of a year.
4. September is the _____ month of a year.
5. _____ is the eleventh month of a year.
根据高血压的严重程度不同如何选用治疗药物？
th of a year.