You want hints?
ok
Find out what a circumcentre and a orthocentre is. Google is very helpful.
Now draw a triangle and roughly indicate where C and O. I suggest you draw an acute angled, isosceles triangle to start with.
Now think about the line from BC ot the circumcentre C.
How will the triangle have to change to get this to be the same line as BC to the orthocentre O
This will indicate at least on correct answer.
Now think about it (draw some more triangles) to see if any of the othes needs to be true as well
This took me some time to work out and then to check. It wil take you and brain power too.
Please no one answer over me.