If a carbon atom is bonded to two hydrogen atoms and two carbon atoms, what type of bond must exist between the carbon atoms?
a)single
b)double
c)triple
d)quadruple

a) single

Explanation:

The carbon atom is a tetravalent element. It has four valence electrons. The valence electrons   can be shared with another atom. Due to high valence electrons, it is easier for the carbon atom to share its four electrons than to lose or gain four electrons. Therefore, carbon forms covalent bond with others. In the given question, a carbon atom combines with two hydrogen atoms and two carbon atoms. Thus 4 electrons of carbon combines with 2 hydrogen atoms and 2 carbon atoms. Thus, single bond will exist between the carbon atoms.