燕王朱棣打着“靖难”旗号，起兵反对建文帝。“靖难”的含义是[ ]
A．最大的困难
B．平定祸难
C．灾难的核心
D．克服困难
答案：B
Your usual teacher has lost his voice and________I am taking his place today.
A．nevertheless
B．however
C．moreover
D．accordingly
《砌体结构工程施工质量验收规范》对砂浆使用时间有哪些要求？
