Final answer:
This question is about the manufacturing tolerance of vents in millimeters and its range of acceptable sizes.
Step-by-step explanation:
The subject of this question is Mathematics at a High School level.
The question mentions manufacturing tolerances for vents that should be 691.15 millimeters (mm) with a tolerance of within 3.15mm. This means that the actual range of acceptable vent sizes is between 688mm and 694.3mm.
The given options (a)1 mm and (b) This does seem reasonable, since the lead does seem to shrink a little when you push on it, are unrelated to the topic and can be ignored.