The "fools" mentioned in the poem "Trees" are D) poets. The poem described trees as beautiful things by comparing it with several conditions in life. Joyce Kilmer also compared the trees to poems and compared their creator, God and poets, which is the main idea of his poem. He compared God and poets with their ability to create as a creator that concluded poets are fools because they can not create a poem lovely as a tree which can only be created by God.