$\begin {array} {1 1} (A)\;diameter = \large\frac{length \: of \: thread}{number \: of \: turns} & \quad (B)\;diamter = \large\frac{number \: of \: turns}{length\: of \: thread}\\ (C)\;\text{by number of turns} & \quad (D)\;\text{ by length of thread} \end {array}$