Which of following is used in pencils as a lubricant?

Which of following is used in pencils as a lubricant?

مندرجہ ذیل میں سے کون سا پنسلوں میں چکنا کرنے والے کے طور پر استعمال ہوتا ہے؟
Explanation

Graphite is a crystalline form of the element carbon.

It consists of stacked layers of graphene.

Graphite occurs naturally and is the most stable form of carbon under standard conditions.