Answer:
Silicon, oxygen and one or more metals
Step-by-step explanation:
Most abundant (mass percent) mineral compounds in the earth crust are:
Silicon dioxide (SiO₂) with a abundance of 42.86%
Magnesium oxide (MgO) with a abundance of 35.07%
Ferrous oxide (FeO) with a abundance of 8.97%
Aluminum oxide (Al₂O₃) with a abundance of 6.99%
So, as you can see the silicon and the oxygen (in the form of oxides) are the most the most common elements found in earth crust, followed by other metal compounds.