Yes it is a reliable source
Explanation: it shows the earth all in one. Makes it easier to study
The Earth's geosphere is made up of iron, oxygen, magnesium, and silicon. All of these elements are chalcogens, or chemical elements.
Answer: approximately 6.28 m
Explanation: C = 2 π r
D = 2 r
C = d = π x 2 ≈ 6.28319 m