How does a writer effectively express an idea about a topic?
a the writer states opinions that are not supported with facts.
b the writer states several thesis statements in the essay.
c the writer states one thesis statement in the introduction.
d the writer adds several new facts in the conclusion.

the writer states one thesis in the introduction so as to clearly express their idea and not confuse the reader

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.