Answer: B- Diametral pitch
The module is the reciprocal of the diametral pitch.
A module of a gear is the ratio of the pitch circle diameter (D) to the number of teeth (T) on the gear. It is usually denoted by “m”. The module is usually expressed in units of "mm.”
m = D/T
The diametral pitch of the gear is a ratio of the number of teeth on the gear to the pitch circle diameter. It is given as,
From the above expression, it is clear that the module is the reciprocal of the diametral pitch.