3 I think Big Al is funnier than the funniest artist of all. His picture is more interesting / the most interesting than Carla's picture.

Решение:

В предложении 3 сравнивается, кто из художников смешнее, а затем сравнивается интересность картин. Правильный вариант выделен.

I think Big Al is funnier than the funniest
artist of all. His picture is more interesting / the most interesting than Carla's picture.