Models of the Evolution of Structure in the Early Universe $\rightarrow$

Multiple Choice

Models of the evolution of structure in the early universe fall into the categories of "bottom-up" formation (stars $\rightarrow$ superclusters) or "top-down" formation (large sheets $\rightarrow$ galaxies and stars) . What parameter in the assumptions for the model is most important in determining which one of these scenarios results?

A) whether dark matter is hot or cold, cold dark matter resulting in the top-down scenario
B) whether dark matter is hot or cold, hot dark matter resulting in the top-down scenario
C) whether neutrinos have mass, massless neutrinos resulting in the top-down scenario
D) whether the early universe had an abundance or a scarcity of metals, an abundance resulting in the bottom-up scenario