$\text{1.}$ C
$\text{→}$ Dòng 1, đoạn 1: Good teeth have us chew our food.
$\text{2.}$ C
$\text{→}$ Dòng 3, 4; đoạn 1: This happens after germs and bit of food have collected there. Then the decay slowly spreads inside to the tooth.
$\text{3.}$ B
$\text{→}$ Dòng 1, 2; đoạn 2: First, we ought to visit the dentist twice a week. He can fill the small holes in our teeth before they destroy the teeth.
$\text{4.}$ D <mik nghĩa là A và C>
$\text{→}$ Dòng 1, 2; đoạn 3: Secondly, we should brush our teeth with a toothbrush and fluoride toothpaste at least twice a day - once after the breakfast and once before we go to bed.
$\text{→}$ should = ought to
$\text{5.}$ D
$\text{→}$ Dòng 1, 2; đoạn 4: Thirdly, we should eat food that is good for out teeth and our body: milk, cheese, fish, brown bread, potatoes, red rice, raw vegetables, and fresh fruits.
$\text{→}$ 3 từ đầu là nên ⇒ từ cuối là ko nên
