1. 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@