Inner core, outer core, mantle and crust
Alvin was a deep sea vehicle which was used to explore the depths of the ocean. It sunk but was recovered and recommissioned in 1973 after which it discovered black smokers, a special type of hydrothermal vent which produces super heated water with a highly acidic pH. Thus, the answer is B.
Metaphase. During metaphase, spindle fibers attach to the centromere of each pair of sister chromatids The sister chromatids line up at the equator, or center, of the cell. The spindle fibers ensure that sister chromatids will separate and go to different daughter cells when the cell divides
