The answers would be:
Hydrosphere and biosphere respectively.
If you'd like to know why:
Your clue would be "river," for the first one. The river and other bodies of water make up the hydrosphere. The second one on the other hand is "organic matter." Although it does say dead organic matter, these were once living things. The sphere that is involved when it comes to living things, as the name suggests, is the biosphere.
