Electrovalent bond or ionic bond is formed by:
A. sharing of electrons
B. donation of electrons
C. transfer of electrons
D. none of these

Hint:Ionic bond is formed between two atoms to attain the stable configuration by donating electrons or by accepting electrons to form cation or anion which are held together by electrostatic force of attraction.

Complete answer:The electrovalent bond is a bond in which the chemical bond is generated by the complete transfer of electrons between the atoms where one atom donates to form positive charge and another atom accepts the electrons to form negative charge. Both the charges are held together by the electrostatic force of attraction in an ionic bond.
By losing the electrons or by accepting the electrons, the atom can achieve their stable configuration.
The electrovalent bond or ionic bond is formed between metals and nonmetals. The bond is not formed between two metals or two non-metals.
The compounds which consist of a positive charge cation and a negative charged anion joined together by an ionic bond by electrostatic force of attraction between them are called ionic compounds.
Examples of ionic compounds are sodium chloride NaCl, potassium chloride KCl.
The ionic bond is formed between the two atoms where the electronegativity difference is very high.
Thus, Electrovalent bond or ionic bond is formed by transfer of electrons.
Therefore, the correct option is C.

Note: The electrostatic force of attraction decreases the potential energy, thus the potential energy of the compound is much less than it was before the generation of ionic bonds.