Answer:
Fossil B belongs to the same period as the trilobite.
Step-by-step explanation:
The Law of Superposition states that the youngest rocks will always be found on top of older rocks. So as you dig deeper and deeper, the rocks you find will be older and older.
An illustration of the problem:
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Fossil C: Two Semi-circles (Top Layer = Youngest)
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Fossil B: Rhombus with Diagnonal & Trilobite (Middle Layer)
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Fossil A: Shaded Rhomboid (Bottom Layer = Oldest)
So, Fossil A is older than both B and C, or, B and C are both younger than A.
Fossil B is Younger than Fossil A, but older than Fossil C.
Fossil C is the youngest (because its on top).