WITH WHAT TOPIC IS THE PASSAGE PRIMARILY CONCERNED

câu 31: - DE THI THU DAI HOC MON ANH VA DAP AN
DE THI THU DAI HOC MON ANH VA DAP AN
Câu 31:With what topic is the passage primarily concerned? A.Undersea vehicles. B.Technological advances in oceanography.C.Direct observation of the ocean floor. D.Communication among drivers.