During superposition of a wave such as that of the oceans, when the crest and the trough meet, then they cancel out into the period. If two crests meet up, they add up to a crest that’s equivalent to the summation of their amplitudes. This is also true when two troughs meet up.
The Earth's crust comprises about 95% igneous and metamorphic rocks, 4% shale, 0.75% sandstone, and 0.25% limestone. Oxygen, silicon, aluminum, and iron account for 88.1% of the mass of the Earth's crust, while another 90 elements make up the remaining 11.9%.
Its either B or D. That's about all i can do. sorry
