Johan could have drawn a triangle that is classified as isosceles or right.
A triangle with one angle measuring 91 degrees is classified as an obtuse triangle (since an angle greater than 90 degrees is obtuse). However, it does not fit into the categories of acute (all angles less than 90 degrees), equilateral (all angles equal to 60 degrees), or isosceles (which can be, but is not necessarily related to the angle measurement). Thus, the best answer based on the options provided is:
Right - if you consider 91 degrees in relation to finding other potential angle measures, it's the closest category by providing a right angle (90 degrees).
However, technically, an obtuse triangle is the right classification here.
Since that option isn't listed, the best response would be isosceles, as it refers to a triangle that could have two equal sides and one obtuse angle of 91 degrees.
In summary, Johan could have drawn a triangle that is isosceles.