The operation Θ is defined by x Θ y = 1/x + 1/y for all nonzero numbers x and y. If z is a number greater than 1, which of the following must be true?

I.

\hspace{10} z \hspace{2} \theta \hspace{2} (-z) = 0II.

\hspace{10} z \hspace{2} \theta \hspace{2} \frac{z}{(z-1)}= 1III.

\hspace{10} \frac{2}{z} \hspace{2} \theta \hspace{2} \frac{2}{z}= zA. I only

B. I and II only

C. I and III only

D. II and III only

E. I, II, and III

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