1. Houston’s study, WHICH dates back to the late 1980s, was extremely influential.
2. The questions were sent to all PARTICIPANTS, WHO answered them by e-mail.
3. Both issues are so intertwined as to be inseparable. CORRECT
4. Ninety-five students were interviewed, and each of the interviews WAS digitally recorded.
5. Our findings suggest that students enjoy both grammar and pronunciation. They seem to believe that the former is as important as the latter. CORRECT
6. Climate change poses a real threat to future generations. CORRECT