Student's Book. Answer key page 17

Exercise 4
 1. have openened, E-books for University Students.
 2. hadn't finished, Oldest Students.
 3. have registered, Biggest School.
 4. has been solving, Young Genius
 5. had been complaining, Teens Wake Up Later
 6. had cheated, University Scandal

Exercise 5
 1. wrong (has been teaching)
 2. correct
  3. wrong (has been studying)
 4. wrong (has been written)
 5. correct
 6. wrong (have been studying)  

Grammar Challenge
1. I've never taken/ done an online course (before)
2. After Alice had had dinner, she revised for her test
3. I've been going to secondary school for two years/ I've been at secondary school for two years.
4.How long has the teacher been talking?
5. By the time I arrived, Jack had been sleeping for an hour