Find out the next number in the given sequence.

$1, 3, 6, 10,$ _____

The numbers obtained by adding consecutive numbers are called triangular numbers.
The first triangular number is $1$. The next one is $3$. 

Further, we get,

 $1+2+3=6$

$1+2+3+4=10$

$1+2+3+4+5=15$
Hence, the next triangular number after $10$ is $15$ i.e the correct answer is option B.