Answer: Option (c) is the correct answer.
Step-by-step explanation:
Moh's scale is used to detect the harness of a mineral. This scale displays harness of 10 minerals.
According to Moh's scale, the hardness of minerals given in the option are as follows:
- Topaz = 8
- Talc = 1
- Diamond = 10
Graphite is not included in Moh's scale.
Thus, we can conclude that the hardest known mineral is diamond.