_______ the calculation is right, scientists can never be sure that they have included all variables and modeled them accurately. 

 A. Even if        B.  As far as       C. If only     D.  So long as

_______ the calculation is right, scientists can never be sure that they have included all variables and modeled them accurately. 

_______ the calculation is right, scientists can never be sure that they have included all variables and modeled them accurately. 

A．Even if            B．As far as           C．If only            D．So long as

_______ the calculation is right, scientists can never be sure that they have included all variables and modeled them accurately.

1. A.
   Even if
2. B.
   As far as
3. C.
   If only
4. D.
   So long as

_____ the calculation is right, scientists can never be sure that they have included all variables and modeled them accurately.

A. Even if      B. As far as     C. If only       D. So long as