There is an elephant and a monkey. They're friends. But one day they want to know who is stronger. One of them says, "Who can get apples over there, who is stronger." There is a river over there. The monkey says, "I can't swim." The elephant says, "I can swim. Please sit on my back." They go across the river. The apple trees are very tall. The elephant can't reach the apples. The monkey climbs up the tree and gets many apples. Now they know they should help each other. The elephant and the monkey want to know   _  .
who is smarter who is higher who can swim who is stronger