Answer:
Oxygen
Step-by-step explanation:
The earth has been divided into three major categories crust, mantle, and core which are further segregated into sub-parts. Since the crust is the outermost layer of the shell, the outer crust of the earth consists of a combination of silicon and oxygen in the majority followed by some percentage of other metals as well. The percentage of Oxygen includes nearly 50% i.e. 46.6% followed by 27.7% of Silicon and the other 25.3 % includes aluminum, iron, sodium, magnesium, etc. Thus, 'oxygen' is the correct answer.