13. You won’t find a good solution ______ you put your heart into the project on environment.

　　A) unlessB) ifC) thoughD) because

　　14.  Jenny often thinks of herself, ________ her sister, Mary is very friendly to others.

　　A) soB) butC) andD) or

　　15. The old man still coughed a lot  ________ he took some medicine.

　　A) ifB) sinceC) becauseD) although

　　16. The brave firemen didn’t stop working _______ all people were saved.

　　A) until

　　B) because

　　C) since

　　D) if

　　17. John didn’t give up looking for his son ________ the police sent the boy back.

　　A) untilB) sinceC) afterD) while

　　18. We should learn from our mistakes ________ we won’t repeat them.

　　A) so … thatB) so thatC) as soon asD) now that

　　19. Some citizens grow vegetables themselves ______they are worried about the safety of the food.

　　A) ifB) althoughC) untilD) because

　　20. You’d better take the GPS with you ________you won’t get lost.

　　A) as soon asB) so thatC) because D) now that

　　21. The organizer (主办方)decided to cancel the concert _______ the tickets didn’t sell very well.

　　A) if  B) until   C) although    D) because

　　22. ______ the government has promised to improve road safety, little has been achieved so far.

　　A) IfB) AlthoughC) UnlessD) Because

　　23. The house was just what I wanted, ______ it was the right price.

　　A) orB) butC) andD) so

　　24. Jenny won’t tell the secret to anyone ______ she knows many people are eager to find it out.

　　A) thoughB) sinceC) becauseD) but

　　25. _______ it rains this Saturday, we’ll have a picnic in Century Park.

　　A) If B) UnlessC) BecauseD) When