on the top of the mountain is an ancient tower dating back to hundreds of years ago .

       A．To stand B．Having stood   C．Standing D．Stand

 ________ on the top of the mountain is an ancient tower dating back to hundreds of years ago .

         A．To stand   B．Having stood    C．Standing   D．Stand

       on the top of the mountain is an ancient tower dating back to hundreds of years ago .

       A．To stand             B．Having stood      C．Standing             D．Stand

 ________ on the top of the mountain is an ancient tower dating back to hundreds of years ago .

1. A.
   To stand
2. B.
   Having stood
3. C.
   Standing
4. D.
   Stand