69. A．and                      C．or

              B．yet                      D．while

　　70.        A．samples               C．origins

              B．sources               D．precedents

　　71.        A．stood by               C．stood against

              B．stood for               D．stood over

　　72.        A．exchange          C．switch

              B．bypass               D．interact

　　73.        A．their               C．when

              B．that                      D．whose

　　74.        A．expanded   C．attracted

              B．contracted D．extended

　　75.        A．what               C．these

              B．which               D．them