How is hardness defined when identifying minerals?
ability to resist scratching
ability to scratch
density of a mineral
organization of crystals
size of crystals

Option (A)

Explanation:

The hardness of a mineral is defined as the ability to resist scratching. Weaker minerals easily get break down when scratching with a less hard mineral. Hard minerals are not easily scratchable.

In order to determine hardness, a scale was developed by Mohr, which is known as the Mohr's hardness scale. According to this scale, the hardness is measured on a scale from 1 to 10. They are given below in the increasing order-

Talc < Gypsum < Calcite < Fluorite < Apatite < Feldspar < Quartz < Topaz < Corundum < Diamond.

The least hard mineral is Talc and the strongest mineral is Diamond.

Thus, the correct answer is option (A).

what's the rest of the question

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.