Answer:
B. shared; atoms
Step-by-step explanation:
Covalent bond is formed by sharing of electrons between two atoms. In this way full outer shell is achieved by both the atoms. Since there is no gain or loss of electrons, no ions are formed in the process.
It is usually formed between the atoms of similar electronegativity. It can be of many types like sigma bond, pi bond etc. If a pair of electrons is shared, it's a single bond. If two pairs are shared, it's a double bond and if three pairs are shared, it's a triple bond.