1.The children sang ....... during the trip. a/happily b/happiness c/unhappy d/happy 2.Water .......... in the lake has made the fish die. a. pollution b. pollute c. polluted d. polluting 3. If we use water carefully, more people ........... fresh water. a. have b. will have c. having d. had 4. Viet Nam is ........ multicultural country with 54 ethnic groups. a. a b. an c. the d. A and C are correct Em cần gấp ạ. Cảm ơn mọi người