Choose the correct answer.

83. Nobody has any firm information, so we can only __________ on what caused the accident.

84. Cars have been banned from the city centre, which makes the area much safer for __________ .

85. There has been a real boom in __________ electronics over the last three decades.

86. When I realised that I'd left my homework at home, I quickly __________ back to get it.

87. I know it's got his name on the cover, but he used a __________ .

88. The text doesn't give you the answer explicitly - you have to __________ it from the evidence.

89. Are you having a __________ exam before you sit the actual exam in June?

90. I couldn't decide what to write about, when I suddenly __________ upon the idea of doing something on writer's block.