The fossil in the picture is a trilobite that lived about 500 mya. so, the age of the rock in the picture is million years old. a) at least 500 b) at most 500 c) exactly 500

The correct answer is A) at least 500.

The rocks in which the fossils are found, are more often then not, indicators of the age of the fossil itself. So if the estimate of the fossil's age is 500 MYA then the rock is of at least the same age, most of the time older then the fossil. 

The answer would be (c), mass extinctions