What is one way invasive species enter the Great Lakes?

Thirty percent of invasive species in the Great Lakes have been introduced through ship ballast water. In the early 1990s, the U.S. Coast Guard began requiring ships to exchange their ballast water, or seal their ballast tanks for the duration of their stay.

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Explanation:

5.4%

explanation:

the acceptance rate for harvard is 5.4%. this means only 5 percent of people who apply actually get accepted!

a and b because with the other three, they simplify to something else.