Why boric acid considered as a weak acid

Boric acid is not what is known as a protonic acid meaning it is unable to release the H+ ions by itself. However, it can act as a traditional Lewis Acid so it is considered a weak acid.

Boric acid is not able to release H⊕ ion on its own. It receives ӨOH ion from water molecule to complete its octet and in turn releases H⊕ ions.

It has the chemical formula H3BO3 (sometimes written B(OH)3), and exists in the form of colorless crystals or a white powder that dissolves in water. When occurring as a mineral, it is called sassolite

credit : wikipedia

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.