Answer:
The correct options are 1, 3 and 6.
Explanation:
Circumcenter of a triangle:
1. It is the intersection point of perpendicular bisector of at least two sides of the triangle.
2. It is the center of the circle that passes through all vertices of the triangle.
It is given that the H Is the circumcenter or a triangle DEF. It means H is the center of the circle that passes through the points D,E,F.
Option 1 is correct.
HD,HE and HF are radius of the circle,

Option 3 is correct.

Option 6 is correct.
Therefore the correct options are 1, 3 and 6.