Question 12

an allotrope of carbon that is soft and can be used as a lubricant is

a)diamond

b)graphite

c)sand

d)silicon

Graphite is the only allotrope of carbon which is acts as lubricant and it is soft in texture.

Option: B

Explanation:

The atoms of graphite are set in a hexagonal structure. Graphite is soft because the atoms are bounded by Van deer Waal forces which are week.

This graphite is called as dry lubricant as the carbon atoms are loosely packed and free to move hence, it is used as lubricant. As graphite is a dry lubricant this can be used where wet lubricant is not being used. It is only non-metal which is electrically conductive.  

answer:   option a) glucagon was secreted by his pancreas before he ate the cookies because blood glucose was low. insulin was secreted after he ate the cookies because his blood glucose was high.

explanation:

d we did this already