All but one description applies to the structure of rna. that is a) four nitrogenous bases. b) double-stranded molecule. c) contains a phosphate group. d) 5-carbon sugar called ribose.

double  stranded  molecule does  not  describe the  structure  of RNA. Most  RNA  are  single  stranded  with  partial  double  stranded  regions.  RNA  has  basic   component  as  the  DNA  that  is have  four  nitrogenous  base,  contain  phosphate  group  and  have  5  carbon sugar.

They include lobsters and crabs

Digestion because it removes waste