Answer:
b. hardest: diamond; least hard: talc
Explanation:
According to the the Mohs scale of hardness ; material hardness are arranged using numbers, which higher values indicating increasing hardness level.
From the scale ;
Diamond has a value of 10 which makes it the hardest on the scale
Talc has a vlaue of 1 which makes it the softest.
A picture of the mohs hardness scale is attached below.
