[单项选择]Before the first non-stop flight made in 1949, it () necessary for all planes to land for refueling. A. would be B. has been C. had been D. would have been
第35题: [单项选择]在填土压实施工中,适用于大面积非粘性土回填压实的方法是()。 A. 振动压实法 B. 羊足碾碾压法 C. 内燃夯实机夯实法 D. 蛙式打夯机夯实法 参考答案:A 答案解析:填土压实方法有碾压法、夯实法及振动压实法。平整场地等大面积填土多采用碾压法,小面积的填土工程多用夯实法,而振动压实法主要用于压实非粘性土。