Question

which is formed from two pieces of different metals stuck together lengthwise?
bimetallic coil
coolant
heat pump
furnace

Explanation:

A bimetallic coil is made by bonding two different metals length - wise. When heated or cooled, the two metals expand or contract at different rates, causing the coil to bend. A coolant is a substance used to transfer heat away. A heat pump is a device that moves heat from one place to another. A furnace is a device that generates heat.

Answer:

bimetallic coil