Talc

a. is the hardest known mineral
b. has a mohs hardness of 1
c. has a mohs hardness of 10
d. is harder than quartz

The answer is B, the Mohs hardness is 1.

Explanation

the most common type of reef is the fringing reef. this type of reef grows seaward directly from the shore. they form borders along the shoreline and surrounding islands.

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.