It was not immediately obvious _____ water was to be fundamental to the development of life.

It was not immediately obvious _____ water was to be fundamental to the development of life.

1. A.
   what
2. B.
   that
3. C.
   when
4. D.
   why

It was not immediately obvious _____ water was to be fundamental to the development of life.

   A. what   B. that   C. when   D. why

It was not immediately obvious _____ water was to be fundamental to the development of life.

A．what                    B．that                      C．when                   D．why

It was not immediately obvious _____ water was to be fundamental to the development of life.