【单选题】Being a devoted abolitionist until the end of his life made Thoreau’s life stimulating and compelling. Which of the following statements is not true about Thoreau as an abolitionist?
A.
He wrote several essays, like "Slavery in Massachusetts" (1854) and “ A Plea for Captain John Brown “(1859), to support abolitionist cause.
B.
He helped slaves escape to the North through the Underground Railroad.
C.
He moved into the political forefront only with his defense of John Brown.
D.
He wrote many books about how helpful and necessary slavery is.
【简答题】某混凝土工程,所用配合比为 C : S : G =1:1.98:3.90, W / C =0.。已知混凝土拌合物的体积密度为2400kg/m 3 ,试计算1m 3 混凝土各材料的用量;若采用42.5普通水泥(富余系数为1.13),试估计该混凝土28天强度(已知f 28 = α a ·f ce ·(C/W- α b ),其中 α a =0.46、 α b =0.07,计算结果保留整数)。