1. Avogadro's hypothesis states that: (A) Each atom of oxygen is 16 times more massive than an atom of hydrogen. (B) A given compound always contains exactly the same proportion of elements by mass. (C) When two elements form a series of compounds, the ratios of masses that combine with 1 gram of the first element can always be reduced to small whole numbers. (D) At the same temperature and pressure, equal volumes of different gases contain an equal number of particles. (E) Mass is neither created nor destroyed in a chemical reaction.