Which of the following is a correct pair of singular and plural?

The correct answer is Option (1) → Basis : Bases

Plural of nouns ending in -is:

Nouns ending in -is change -is to -es in the plural. So basis → bases. A basis is the main idea or fact on which something is built.

Why the Other Options are Incorrect?

Option 2: Axis : Axises — Incorrect. Axis also ends in -is, so it follows the same rule. Axis → Axes.

Option 3: Child : Childs — Incorrect. Child has an irregular plural. It adds -ren, not -s. Child → Children.

Option 4: Piano : Pianoes — Incorrect. Piano takes only -s. Piano → Pianos.