are placed on dangerous machinery to detect motion, light, heat, pressure, or another stimuli. Their presence helps protect operators from injury while working on machines. Mirrors Labels Sensors Alarms

the answer is b: a lockout

explanation:

i believe the primary and secondary sectors

productive most commonly means: achieving or producing a significant amount or result.

explanation:

productive can also mean:

these depend on how the word productive is used. most likely productive will mean   achieving or producing a significant amount or result.