III. Change these sentences to the passive voice :
91. Don’t ask for another book until you finish this one.
92. Her father was planting different kinds of flowers in the garden.
93. The Prime Minister is making a speech at the moment.
94. How many days did she spend finishing the work?
95. The doctor pulled out one of my teeth yesterday morning.
96. His wife usually brings him sandwiches at lunch time.
97. The light went out while I was making a cup of tea.
98. The students of chemistry made many experiments last week.
99. For the past years, I have done all my washing by hand.
100. A pair of robins has built a nest in the porch since last week.