Cng cylinders must be inspected at least every a) month b) year c) 12 months or 12,000 miles d) 36 months or 36,000 miles

36 months or 36,000 miles

Explanation:

CNG cylinder has limited lifespan. Generally lifespan of CNG cylinder is 15 years to 20 years. For safety purpose these cylinder should be inspected timely. Time limit for inspection of CNG cylinder is 36 months or 36,000 miles whichever comes first.

ThusCng cylinders must be inspected at least every 36 months or 36000 miles.  

1 is a answer of a question