WITH WHAT TOPIC IS THE PASSAGE PRIMARILY CONCERNED

61. - DE THI THU DH THAN KHAO CO DAP AN
Tiếng Anh DE THI THU DH THAN KHAO CO DAP AN
61. With what topic is the passage primarily concerned?A. Communication among drivers. B. Direct observation of the ocean floor.C. Undersea vehicles. D. Technological advances in oceanography.