Question

typically, saltwater fish cannot survive in freshwater. similarly, most freshwater fish 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.
the population of diadromous fish is in decline across the atlantic.
conservation efforts exist to protect diadromous fish facing barriers to migration.

Explanation:

To solve this, we need to find the sentence that logically connects the first part of the passage (about diadromous fish in general and their ability to adapt) to the example of striped bass (and other details about their life cycle and migration).

Analyzing each option:

1. Option 1: Talks about the two categories of diadromous fish. The next part (after the blank) is an example of striped bass’s life cycle, not a discussion of categories. So this is not a good fit.
2. Option 2: States that many diadromous fish move between habitats during development or certain times of year. The example of striped bass (born in freshwater, move to estuaries, then to the ocean, then back to freshwater to spawn) directly illustrates this movement between habitats. This connects the general idea of diadromous fish’s adaptability to a specific example of their migration.
3. Option 3: Discusses the decline of diadromous fish. The next part is about the striped bass’s life cycle, not about population decline. So this is irrelevant.
4. Option 4: Talks about conservation efforts. The next part is about the striped bass’s life cycle, not about conservation. So this is also irrelevant.

The sentence after the blank gives an example of striped bass moving between freshwater, estuaries, and the ocean. The option "Many move between habitats during periods of development or certain times of year" introduces the general idea of diadromous fish moving between habitats, which the example illustrates. Other options (about categories, population decline, or conservation) do not connect to the example of migration/habitat movement.

Answer:

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