.

. All books ___________ to the library more than three days late will be subject to a fine.

    A. return        B. returning             C. to return      D. returned

31. All books ______ to the library more than three days late will be subject to a fine.

   A. return                   B. returning              C. to return              D. Returned

31. All books ______ to the library more than three days late will be subject to a fine.