<span>The layer of rock above it might contain the fossil of a fish as, according to the law of faunal successsion, this was the first animal to evolve after shelled organisms. In sedimentary rock, animals that evolved later could only be found in layers above those from an earlier time.</span>
Chlorine has a charge -1. It means that X is +2 so that the formula is XCl2. Group 2 is the correct answer.
