The burrows of these early crustaceans that once lived during the Jurassic Period are examples of fossils? A.concrete
B.index
C.trace
D.trail

C. Trace

Explanation:

Generally, fossils are the mineralized or preserved remains of a previously existing organism. Fossils, which show how long an organism has been in existence, can include but not limited to bones, DNA, shells, footprints etc. However, fossils can either be the actual organism's remains or a recorded impact of the organism called TRACE FOSSILS.

Trace fossils are those fossilized impacts such as burrows, footprints that suggests the presence of the organisms that created or formed them. Hence, in this case, the BURROWS of early crustaceans that once lived during the Jurassic Period are examples of TRACE FOSSILS.