Assertion:Hydrogen combines with other elements by losing, gaining or sharing electrons.
Reason:Hydrogen forms electrovalent and covalent bonds with other elements.
A.Both assertion and reason are correct and reason is the correct explanation for assertion
B.Both assertion and reason are correct but reason is not the correct explanation for assertion
C.Assertion is correct but reason is incorrect
D.Both assertion and reason are incorrect

Hint: hydrogen combines with most of the elements in the periodic table. On combining with the elements, hydrogen forms hydrides. Hydrogen is a very reactive element. It forms electrovalent and covalent bonds.

Complete answer:
Hydrogen completes its octet by sharing only two electrons unlike other electrons that complete their octet by sharing eight electrons. Hydrogen forms both electrovalent and covalent bonds.
Electrovalent bonds are the bonds that are formed when electrons are transferred from atoms of one element to atoms of another element, producing positive and negative ions. This bond is also known as an ionic bond.
Covalent bonds are the bonds that involve the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs.
Hydrogen also combines with other elements using electrovalent bond and covalent bond. It forms electrovalent bonds by losing or gaining electrons and forms covalent bonds by sharing the electrons. Thus both assertion and reason are true.

Therefore the correct option is A. Both assertion and reason are correct and reason is the correct explanation for assertion.

Note:
Hydrogen element actually does not follow octet rule as it cannot have eight electrons in the outermost shell and therefore it follows another rule which is called the duplet rule, which says that the element can attain stability even with two electrons in the valence shell. Hydrogen attains stability by following the duplet rule. Other than hydrogen, helium also follows the duplet rule.