The main conflict in the speaker's mind in "Birches" is that (C) between childhood and adulthood. Everytime the speakers sees a bent birch tree, he thought of it that it is caused by the boys swinging on it where in fact it is far from the real reason - and he knows it. When he was a kid, he used to see it but now that he's adult, he used to think of it again where in fact it caused by natural phenomenon.
