Which of the following statements regarding Medigap plans are CORRECT?

I. Medigap policies may duplicate benefits provided by Medicare.

II$.$ Retirees may not be turned down for a Medigap policy as long as it is applied for within six months of enrolling for Medicare or when their existing coverage lapses.

III. $10$ approved plans are available.

A$.$ I, II$,$ and III

B$.$ II only

C$.$ Ill only

D$.$ Il and III