Final answer:
The correct term for the diameter at the base of the groove is 'Width,' according to principles of groove design in engineering, thus making 'C) Width' the right answer.
Step-by-step explanation:
The proper diameter at the base of the groove refers to the overall size of the groove's width at its most extensive point. Traditional guidelines for the design of grooves in engineering suggest a ratio of width to depth where the width is often scaled by the diameter.
An old “rule of thumb” was 5 diameters wide side-to-side and 7-8 diameters deep, whereas contemporary research points towards larger dimensions, recommending as much as 8 diameters wide side-to-side and 15 diameters deep. This information implies that the proper term for the diameter at the base of the groove is the 'Width' of the groove. Therefore, the correct answer to the question is C) Width.