6. When two oceanic plate boundaries meet, what crustalfeature forms(see photo below)
A Plate Tectonics
B. Sea Floor Spreading
C. Folded Mountains
D. Volcanic Island Arc

Both models are effective because they show the valence electrons, and these valence electrons indicate the reactivity of an element.

2significant figures

All you need to do for this is to understand what the person meant in their quotes, and to understand what entropy is. after that just compare the two.example: person mcguy, states that entropy is "persons idea of entropy". compared to todays studies, and terms  it differs from today, because "why it differs, and what scientists use, and understand entropy as." for this you can pretty much just look up a modern definition of entropy to get the necessary "today's view on the word."