When heated in air, coal burns and produces mainly ___ gas.
Coal burns in air to form mainly:
(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.
(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.
(e) Forests and coal are ______ natural resources.