单项选择题
The words PIPE，BUTT，TUN AND PUNCHEON all refer to（）.
A.the sizes of casks B.various lengths of timber C.structural shapes used in construction D.viscosities of liquid cargoes
单项选择题 The welds used to join shell plates in flush construction are known as（）.
单项选择题 The welds used to attach stiffeners to a plate are known as（）.
单项选择题 The type of joint formed when an edge of one plate is laid over the edge of the plate to which it is riveted is a（）.
