Question 4: A. had graduated

Question 5: B. once its construction is completed

Question 6: D. have fixed

Question 7: B. until he contracts the virus

Question 8: C. had been told

Question 9: B. has been teaching

Question 10: A. when she has returned from her business trip

Question 11: B. had arrived

Question 12: B. Do-lock

Question 13: C. since we started working from home

Question 14: D. until she gets a parking permit

Question 15: B. once their son gets the first prize in the English-speaking test