Einstein had written to inform Roosevelt that recent research on fission chain reactions utilizing uranium made it probable that large amounts of power could be produced by a chain reaction and that, by harnessing this power, the construction of "extremely powerful bombs" was conceivable.
Einstein wrote a a letter to Franklin D Roosevelt ,the American president warned him that a single nuclear bomb would make a mass destruction. It was the fact that the Nazis had the ability to develop the atomic bomb. It could destroy the whole world. So he warned Franklin D Roosevelt in his letter.
A is the only adjective or describing situation; describing how she looked while the others use the adverb cheerfully to describe further the verb that came before it.
