Question

when should the blade of a utility knife be replaced?
a. once every five years
b. when it gets dirty
c. once a year
d. when it stops cutting and starts tearing materials

Explanation:

A utility knife blade's replacement is based on its functionality. A dirty blade can be cleaned, and fixed time intervals (like 5 years or 1 year) don't account for usage. When the blade stops cutting properly and tears materials, it's no longer effective, so it should be replaced.

Answer:

D. When it stops cutting and starts tearing materials