A river flowing downhill transports matter toward its base matter can be dissolved in the water or can be in the form of sediment which form of matter would be dissolved in water a sand b leaves see pebbles d minerals

d. Minerals

Explanation:

Among the options mentioned in the question sand, leaves and can not dissolve in water rather they can form sediments. Only minerals can dissolve in water because in minerals there are different types of elements which can form ions when they are dissolved in water. These ions get bonded with the Hydrogen of Oxygen in the water molecules and thus they will form a uniform solution which in simple terms can be said that minerals have ability to get dissolved in water.