1) Only D is correct. "makes a number of advantages" may appear to make sense, but it is not idiomatic. 2) "on" and "at" both work.
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Nguyen Dat#2 "on" and "at" both work but there is any difference between them?Any difference is hair-splitting or debatable. You could perhaps argue that "on" more strongly implies that the antenna is the highest part of the structure.