If a carbon atom is bonded to two hydrogen atoms and two carbon atoms, what type of bond must exist between the carbon atoms?

The bonds between the carbon atoms must be single bonds.

Explanation: Carbon is a non metal which have an atomic number of six and four valence electrons. Atomic number is the number of protons in the nucleus of an atom. The number of protons in an atom is equal to the number of electrons in the same atom. This means that carbon has six electrons, four out of the six electrons are found in the outermost shell and hence are called valence electrons.

The number of valence electrons of an atom determines the maximum number of bonds an atom can form with other atoms. Therefore, carbon atoms can form a maximum of four bonds with other atoms.

Since the carbon atom is bonded to two hydrogen atoms and two carbon atoms giving a total of four atoms, the type of bond between the carbon atoms is single bonds.

See the attached diagram

atp is used for energy.