Question

The original source of all sand is:
beaches
oceans
rocks
rivers

Answer 1

The composition of sand varies, depnding on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal settings is silica (silicon dioxide, or SiO2), usually in the form of quartz. But mostly you can just say for an answer it comes from rocks.

Answer 2

The original source of all sand is rocks.

There are various types of rocks and some rocks are broken down into pieces which leads to become sand. Moreover, sedimentary rocks are formed by the layers of deposition that takes place. The main difference between a sedimentary rock and sediment is that in case of sedimentary rocks the sediments are stuck together to form a hard rock like structure and sediments are normally loose in nature.