Because sediments sometimes include once-living organisms, sedimentary rock often contains a lot of fossils.
(sediments; include; once-living organisms, sedimentary rock often contains a lot of fossils; T:sometimes) (sedimentary rock; contains; a lot of fossils; T:often)
sediments sedimentary rock
include contains
once-living organisms, sedimentary rock often contains a lot of fossils T:sometimes
a lot of fossils T:often