(a) Coal is one of the ______ used to cook food.
(2)
Fill in the blanks in the following sentences.
(b) When heated in air, coal burns and produces mainly ______ gas.
(3)(c) Coal tar is a black, thick ______ with an ______ smell.
(4)
Fill in the blanks in the following sentences.
(d) Petroleum, ______ and ______ are fossil fuels.
(5)(e) Forests and coal are ______ natural resources.