The correct option is
D
In the pattern given above, each blue triangle has one more row of white triangles inside them than the previous one.
Also, the number of white triangles in the second row is one more than the number of triangles in the first row, if the blue triangle has white triangles inside it.
So, the next figure in the sequence will have 3 rows of white triangles and the first row will have 3 triangles.
So the figure that will come next in the pattern is :