The temperature of tempering oil baths maintained at 400°C during heat treatment of steel is measured by a/an ___ thermocouple

The temperature of tempering oil baths maintained at 400°C during heat treatment of steel is measured by a/an __________ thermocouple.

A. chromel-alumel
B. iron-constantan
C. platinum-platinum/rhodium
D. none of these.

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Answer: B

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