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Các công thức đổi HTHT - QKĐ

Structure 1: 

How long + has/have + S+ V3/ed?

--> When + did + S + V1?

--> How long is it + since + S+ V2/ed ?

Structure 2:

S + has/have + V3/ed + for/since + time 

--> S + started / began + to V / Ving 

--> It is / has been + time + since + S+ V2/ed 

Structure 3: 

S + has/have + not/never + V3/ed + ... before

--> This/It is the first time + S+ has/have+ V3/ed

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104. My sister has studied English for a year. 

105. Scientists have been fighting against AIDS since 1980. 

106. The Browns began living in London for 20 years. 

107. John started working for this electronics firm in 1999. 

108. Women began fighting for their rights in the middle of the 20th century. 

109. Jack and Jil started learning to drive 2 weeks ago. 

110. When did you study English?

111. How long have you done research on lung cancer? 

112. This is the first time my father has driven a car. 

113. It's the first time I have met such a famous singer. 

114. It's the first time she has been to the ballet. 

115. This is the first time she has drunk Coca Cola.

116. It's the first time I have read this book. 

117. It's the first time I have met such an intelligent student.