Answer:
Please elaborate more your question so I can answer your question accurately.
Explanation:
The answer Is D.
Copyright save the author Idea so nobody else can use that Idea for their benefit.
Answer: A. Usability testing
Explanation:
Usability testing would be the correct answer because if the user interface isn't "frendly" then people won't be able to use it properly. Or if you are refering to the word friendly as looking safe, then even more so would be usability testing. Because if people don't like the fonts and styles of the user interface, they might not use it at all.
Answer:
A mechanical thermostat will typically use a bimetal strip with two different metals that expand/contract with the temperature at different rates.
Explanation: