Numbers that are obtained by adding consecutive numbers are called ?

The numbers that are obtained by adding consecutive numbers are called triangular numbers.

The first triangular number is $1$. The next triangular number is $3$ i.e $\left(1+2\right)$. The first ten triangular numbers are $1, 3, 6, 10, 15, 21, 28, 36, 45 and 55$.

Square numbers are obtained by multiplying the same number by itself. For example, $9$ is a square number ($3\times 3=9$)

The fibonacci numbers are the numbers that are obtained by adding the two previous numbers.

Therefore, the correct answer is option A i.e triangular numbers.