Question

complete the text with the detail that best develops the main topic.
typically, saltwater fish cannot survive in freshwater. similarly, most freshwater fis cannot adapt to saltwater. there are, however, a few species that thrive in both. these fish are classified as diadromous, a greek term that means
unning across.\ diadromous fish include salmon, american eels, bull sharks, and striped bass. specific characteristics and migration patterns allow these fish to adapt to changes in the waters salt content.
______ striped bass, for example, are born in freshwater. they remain in estuaries, areas where salt and freshwater mix, for up to four years before they enter the salty atlantic ocean. mature fish return to freshwater in the spring to spawn. diadromous fish are incredibly important to both ecosystems they inhabit because they transfer nutrients between freshwater and saltwater areas, effectively balancing these crucial aquatic environments.
there are two categories of diadromous fish, anadromous and catadromous.
many move between habitats during periods of development or certain times of year.
conservation efforts exist to protect diadromous fish facing barriers to migration.
the population of diadromous fish is in decline across the atlantic.

Explanation:

The blank comes right before an example of striped bass's habitat movement through life stages. The correct option must introduce the pattern of moving between habitats tied to development, which sets up the example. The other options either introduce unrelated categories, conservation, or population decline that don't connect to the subsequent example.

Answer:

Many move between habitats during periods of development or certain times of year.