—Thank god, you finally returned home ________. —You can never imagine how I worried about you when I was told about the terrible accident. 

____ to the surprise of the teachers, the naughty boy turned out to be the person who saved the dying girl. 

---Students should devote most of their time to studying rather than playing computer games.                                                       ---________.No pains, no gains.

＿＿＿＿to my regret, I am unable to accept your warm invitation. 

 A Korean survey shows that shopping cart handles are the most bacteria-carrying items among some ________used objects.