71. C. help
12. A. Three
13. B. Volunteering costs a lot of money
14. A. is very useful

75. We keep our bodies warm to avoid the flu and a cold.
16. You should not play more computer games in your free time.
77. Vitamins play an important role in our diet.
78. Getting enough rest helps you concentrate at school.
79. The doctor is asking Huy questions about his health problems.
80. That dog is not as dangerous as it looks.
81. Schools in Viet Nam are different from schools in the USA.
82. They visited Ha Long Bay some years ago.
83. My hat is different from Thu's hat.
84. He has the flu. He keeps sneezing and coughing.

85. Most children like cookies and milk.
86. I don’t like coffee, but I like tea.
87. In Ha Noi, they give warm clothes away to homeless people.
88. Pho is a special kind of traditional Vietnamese dish.
89. Students take part in many outdoor activities during the school year.
90. Volunteering makes a difference in our community.