Why would someone do a comparison/contrast

The greatest gift the sumerians gave the world was the invention of writing. the sumerians were wealthy people. they needed some way to keep track of what they owned. they began drawing pictures. they used a reed as a pen. they drew on soft pieces of clay. the soft clay was then dried in the sun. the tablet became a permanent record. later, the sumerian drawings changed into wedge-shaped symbols. this kind of writing is called cuneiform. by putting symbols together, the sumerians could write entire sentences.

Which statement contains an opinion? the ants serve to protect the acacia from other plants and herbivores. the acacia depends on pollinators for the exchange of genetic material. the acacia has no chemical defenses to discourage herbivores. the ants provide the acacia with the best protection from other plants and herbivores.

Olivia is making scarves each scarf will have 5 rectangles and 2-5 of the rectangles with be purple how many purple rectangles does she need for three scarves