What is theme?
a. poetry that doesn’t follow the rules of a particular poetic template
b. a poetic technique in which one line is carried onto the next
c. a statement about an abstract idea expressed in a work of art
d. writing or speech that is not intended to carry literal meaning

halibut, flounder, tuna, and trout are all fish. so your first answer is 1.) fish. and since fish is edible, your next answer would be 3). edible

to describe those fishes more thoroughly, some of those fishes live in fresh water, and some of the fishes live in salt water, and that is not a thing that they all have in common. the question is asking what is common with all of the fish, so answer choices 2). fresh water and 4). salt water are not right.

the answer is a.

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hope this !