Hola!
We know,
1 Mole of anything has 6.02 ×

particles
According to Question,
6.02 ×

= 1 Mole
Thus,
1.8 ×

/ 6.02 ×

= 0.33 Moles
hope it helps!
I'd say b, but i'm not 100 percent sure.<span />
That number has five significant figures
Nucleus is the answer, I believe