19.What is the average density of marine sediments?
(A) 2.1 g/cm3
(B) 5 g/cm3
(C) 0.3 g/cm3
(D) 28 g/cm3
(E) 1.3 g/m3

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統計： A(0), B(1), C(1), D(0), E(0) #2788467