Could someone help me on number 3.

When coal has reached it hardest, darkest form, it is called select one: 0 a. sub-bituminous b. lignite c. bituminous d. antrhacite next page

The transport tubes from food came down the plant are called?

Pentane with molecular formula c5h12, exists in three isomeric forms. one shows linear carbon chains, another has one -ch3 groups present on the third carbon atom, and the third has two -ch3 groups present on the second carbon atom. what types of isomers are these? a. geometric isomers b. structural isomers c. halotropic isomers