A．exchange C．switch B．bypass D．interact 73. A．their C．when B．that D．whose 74. A．expa

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 76. A．joined C．participated B．attached D．involved

77. A．moreover C．likewise B．however D．then

78. A．With C．In B．By D．As

79. A．contexts C．messages B．signs D．leaflets

80. A．citizen C．amateur B．civilian D．resident

81. A．into C．over B．amid D．toward