(a) 10
Ethyne (C₂H₂) has a triple bond between two carbon atoms (6 shared electrons) and one C–H bond on each carbon (2 × 2 = 4 shared electrons). Total = 6 + 4 = 10 electrons shared.
Count all shared electrons in every bond: the C≡C triple bond shares 6 electrons, and each of the two C–H single bonds shares 2 electrons, giving 6 + 4 = 10. Students often confuse number of bonds (5 bonds total) with number of electrons shared — the question asks for electrons, so multiply bonds × 2.