A covalent bond is possible between:-
E. Similar atoms
F. Dissimilar atoms
G. Similar and Dissimilar atoms
H. Similar molecules

Hint:A covalent bond is formed by the sharing of atoms electrons in equal proportion from both the atoms that are involved in the bond formation. It is basically about the involvement of the electrons and they are known as bonding electrons or shared electrons. The covalent bond is formed so that the atoms involved achieve their stability by completing their octet.

Complete step by step answer:
-Covalent bond is also known as molecular bond which involves the bonding of electrons between two
similar or dissimilar atoms.
-Now let’s take an example to describe the covalent bond formation criteria;
Hydrogen,
Atomic number = $1$
Atomic mass = $1$
-If we write the electronic configuration of the hydrogen atom, we find that it has only 1electron in its
$s$ subshell and need one electron to get stable like our Noble gases in the periodic table.
-Therefore this hydrogen will pair up with another hydrogen atom and will complete its octet
-Hydrogen has the ability not to gain or lose its electrons so it will form a covalent bond with itself.
-Covalent bonds can be formed between carbon and the hydrogen atom of methyl group.
$C{H_3}$
-Now we will discuss some properties possessed by covalent bonds.
-In covalent bonding only sharing takes place not new formations.
-The energy required to break the bond is high.
-They are not easily breakable.
-Covalent bonded compounds do not have free electrons, so they do not conduct electric current.
The correct answer is option C.

Note:
Covalent bond can be of three types depending upon the number of sharing of electrons
 Single Covalent Bond: having only one pair shared.
Double Covalent Bond: having sharing of two electrons
Triple Covalent Bond: having sharing of three electrons.