Which type of bond is formed by two atoms that equally share one pair of electrons?

I am pretty sure that it is called a covalent bond, I hope that I am right.  If not please correct me.

1. and 2. question: in which equation? or i don't understand you, 3. a), 4. c), 5. c), 6. b), 7. d), 8. d) if small number is underlined(behind symbol) , b) if big number is underlined(in front of symbol)9. what is underlined there? 10. c)