Which of the following is not a fourier transform pair?

• A. (u(t) leftrightarrow ( ) + frac{1}{j } )
• B. (sgn(t) leftrightarrow frac{2}{j } )
• C. (A leftrightarrow 2 ( frac{ }{2}) )
• D. (G(t) leftrightarrow sa( frac{ }{2}) )