【单选题】主要依靠墙身自重维持稳定的挡土墙称( )
【简答题】A.50 years. B.100 years. C.200 years. D.300 years.
【简答题】I.1100℃时,在恒容密闭容器中,发生如下可逆反应: Na 2 SO 4 (s)+4H 2 (g) Na 2 S(s)+4H 2 O(g),并达到平衡。请完成下列各题: (1)达到平衡时的平衡常数表达式:K=________;降低温度,K值减小,则正反应为_________(填“吸热”或“放热”)反应。 (2)向该容器中分别加入以下物质,对平衡的影响如何? ①加入少量Na 2 SO 4 ,则平衡...
【单选题】How long will people’s careers be in the future, according to our reading? a. 25 years c. 40 years b. 30 years d. 50 years
【单选题】Keven is ,and he has a sister.
A.
13-year-old; two-year-old
B.
13 years old; two years old
C.
13 years old; two-year-old
【简答题】A.About 20 years. B.About 30 years. C.About 50 years. D.About 40 years.