7. Look at the representation of a hillside below. The symbols in each stratus of the cross-section represent fossils of different organisms. Which of the following organisms must have evolved first?
% * ^ ^ *
% $ $ $ # # # * * * * *
$ * * * $ $ # # # # @
% # # # @ @ ! ! ! ! * *
@ < < < < < + + + + = =
A. $
B. #
C. *
D. @