along shorelines
First, look at the definitions involved. hydrosphere - All the water on earth's surface such as lakes and seas. lithosphere - The rigid outer part of earth's crust. Now look at the available choices: on mountaintops * Bodies of water aren't too common up on mountain tops. Not a good choice. inside glaciers * Inside glaciers? Not touching earth, but lots of ice instead. Also not a good choice. at volcanoes * Not a lot of water here either. Bad choice. along shorelines * Sounds good. The boundary between water and earth. This is the right answer.