85. ___________you ever ___________(ride) a horse before?

84. We ___________ (not see) each other since he ___________ (leave) here.

83. Our teacher told us time ___________ (be) life.

82. These exercises must ___________ (do) by yourself.

81. It ___________ (snow) hard now. We'd better ___________ (not go) home right now.

80. Tennis ___________ (invent) a hundred years ago.

79. English ___________ (speak) in Canada.

78. So far, many man-made satellites have ___________ (send) up into space.

77. The young trees must ___________ (tie) to the stick to keep it straight.

76. The mountain will ___________ (cover) with the trees in a few years.