A trapezoid is a type of quadrilateral that has an opposite pair of parallel sides; at lest, that definition seems pretty accurate to me.
The outer core is more thinner than the inner core. outer core is also more rocky in material.
After looking at the photograph given above, one sedimentary rock that probably metamorphosed to form rock on unit 6 is called limestone. You can also use the sedimentary rock called dolostone. Both will be acceptable answers to this question.
