Question

mantle
mantle is almost 3000 km deep. this layer
consists of metals like _,
_ and silicate rocks. the
approximate percentage of constituent
elements of the mantle layer are as
follows; 45% _, 21%
silicon and 23% magnesium.

Explanation:

The mantle is Earth's layer composed of iron and magnesium-rich silicate rocks. The most abundant element in the mantle is oxygen, making up about 45% of its composition, followed by silicon (21%) and magnesium (23%).

Answer:

1. Magnesium (or iron)
2. Oxygen