Which of the following element found mostly in earth's crust?

Answer: Option A

The element found mostly in earth's crust is Oxygen.
Oxygen is Earth's most abundant element, and after hydrogen and helium, it is the third-most abundant element in the universe. Oxygen makes up almost half of the Earth's crust in the form of oxides.
Oxygen is by far the most abundant element in the Earth's crust, making up 46% of mass coming up just short of half of the total. Oxygen is a highly reactive element that combines with other elements, forming oxides.