When learning the form of proposition, the topic is to prove the truth of proposition, so you only need to prove the truth of four options. We know that proving the true proposition requires a rigorous proof process, while proving the false proposition only needs to cite counterexamples, so this multiple-choice question can be done by exclusion, and the false proposition can be excluded by examples.

When a = 1, b = 1, c = 1, a+ 1/b = 2, b+ 1/c = 2, c+ 1/a = 2.

When a = 1/2, b = 1/2 and c = 1/2, a+ 1/b = 2.5, b+ 1/c = 2.5 and c+/kloc.

So choose D.