He hurried home, never once looking back to see if he_________.
was being followed
was following
had been followed
followed
Had the government limited the sales of cars much earlier, traffic jam and pollution _______so serious now.
____today, he would get there by Friday.
Had they known what was coming next, they _________second thoughts.
Had you taken it more seriously, you ________ such a silly mistake.
_________, the world would be more harmonious.