Which labels belong in the areas marked X, Y, and Z?
A
X: It begins in a nebula. Y: Nuclear fusion forms hydrogen in the main sequence star. Z: A protostar is part of the cycle.B
X: A protostar is part of the cycle. Y: It begins in a nebula. Z: nuclear fusion forms hydrogen in the main sequence star.C
X: A white dwarf is part of the cycle. Y: Nuclear fusion forms hydrogen in the main sequence star. Z: A supernova is part of the cycle.D
X: Nuclear fusion forms hydrogen in the main sequence star. Y: A white dwarf is part of the cycle. Z: A supernova is part of the cycle.