Which transition would a writer use to contrast two ideas?
therefore
furthermore
specifically
although

The correct answer is:  although.   In contrast, transition words tell the reader that the writer is changing from one item to another. Transition words and phrases help to make a softer and more coherent paper by showing the reader the connections between the ideas presented.

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.