, 145. It was a very difficult task. I (to understand) it when I (to read) it several times
146. He (to leave) for Canada before his family moved to this city and (to live) there since then.
147. As she (not to know) what kind of present to give him, she (to ask) her friend for advice.
148. What he (to do) when you (to call on) him?
149.She (to have) that unknown disease since she (to be) 15 years old.
150. Yesterday when I (to walk) along the street I met a friend of mine whom I (not to see) for nearly ten years.
151. He told us that the books (to be brought) the next day, but I (not to see) them so far.
152. She (to want) to know where they (to go) for their holiday.
153. Where you (to work) before you (to enter) the Institute?
154. They (not to meet) ever since they (to graduate) from the University.