单项选择题
A.alternate expansion and contraction as water in a liquid state becomes a vapor
B.absorption of smoke and gases as water is converted from a liquid to a vapor
C.rapid contraction as water is converted from a liquid to a vapor
D.rapid expansion as water absorbs heat and changes to steam
单项选择题 A design modification of an anchor chain which prevents kinking is the（）.
单项选择题 A device fitted over the discharge opening on a relief valve consisting of one or two woven wire fabrics is called a（）.
单项选择题 A device used to enlarge the size of an existing bore hole, having teeth arranged on its outside circumference to cut the formation as it rotates is a (n)（）.