Is it possible for a horse pen to be an acute right triangle

No, because you can't combine 2 different triangles into one triangle.

In any right triangle, the two angles at either end of the hypotenuse
are both always acute angles.

But I don't think that would be called an 'acute' triangle, because an
acute triangle is one in which all three angles are acute ones

Correct sir/miss have a good day x < 3

Iam thinking the answer is a.) knew