( )是决定砌体抗压强度的首要元素。
A. 块材和砂浆的强度
B. 砂浆的性能
C. 块材的尺寸
D. 砌筑质量
一般抹灰使用的块状生石灰须经熟化成石灰膏才能使用，在常温下，熟化时间不应少于( )；用于罩面的石灰膏，在常温下，熟化的时间不得少于( )。
A. 10天，20天
B. 12天，24天
C. 15天，30天
D. 16天，25天
According to the passage water is important for all of the following, except______.
A. early international trade
B. the most common substance in living plant and animal tissues
C. hydroelectric power stations
D. sanitation and recreation
According to the author, technical terms are used because ______.
A. they describe a process in details
B. they can only be understood by people of a given profession
C. they can be found in almost every dictionary
D. they can be universally understood by people of a given profession
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