Which one among the following is true?

• A. \[\sqrt{m}+\sqrt{n}=\sqrt{m+n}\]
• B. \[\sqrt{(m+1)}+\sqrt{(n+1)}=\sqrt{(m+1)(n+1)}\]
• C.  \[\sqrt{m}-\sqrt{n}=\sqrt{m-n}\]
• D. \[\frac{1}{\sqrt{m}+\sqrt{n}}=\sqrt{m}-\sqrt{n}\]
• E. None of these