A solid whose atoms, ions or molecules are arranged in a regular

repeating pattern is considered to

have which of these?

A. a gaseous structure

B. a crystalline structure

C. a liquid structure

D. a plasma structure

one characteristic that is shared by all is a soft body. many

of these invertebrate animals also have an outer shell to protect their

body. oysters, clams, snails, and mussels are all mollusks. so are octopuses, squids, and slugs. mollusks live on land and in freshwater.

the areas around the equator

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".