It never occurred to humans until the mid-l990s            some animals can be cloned.

It never occurred to humans until the mid-l990s            some animals can be cloned.

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

It never occurred to humans until the mid-l990s            some animals can be cloned.

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

. It never occurred to humans until the mid-l990s _______some animals can be cloned.

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

It never occurred to humans until the mid-l990s            some animals can be cloned.

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