题目

与藻类、苔藓植物相比，蕨类植物更适合在陆地上生活的主要特点是（） A . 与苔藓植株相比，植株高大 B . 根、茎、叶内有输导组织 C . 叶背面有孢子囊群 D . 生殖过程离不开水 答案：BIt is very important to have healthy teeth. Good teeth help us to chew our food .They also help us to look nice.How does a tooth go bad? The 1lbegins in a little crack in the enamel(珐琅) covering of the tooth. This happens after germs and bits of food have2 there. Then the decay slowly spreads inside the tooth. In the end, poison goes into the blood, and we may feel quite ill.How can we keep our teeth3? First, we ought to visit our dentist twice a year. He can fill the small holes in our teeth before they destroy the teeth. He can454our teeth to check that they are growing in the right way. 5, many people wait until they have toothache before they see a dentist. Secondly, we should brush our teeth with a toothbrush and fluoride(氟化物) toothpaste at least6 a day—once after breakfast and once before we go to bed. We can also use wooden toothpicks to7between our teeth after a meal. Thirdly, we should eat food that is8to our teeth and our body: milk, cheese, fish, brown bread, potatoes, red rice, raw vegetables and fresh fruit. Chocolate, sweets, biscuits and cakes are bad, especially9we eat them between meals. They are harmful because they10our teeth and cause decay.1.A.destructionB.decayC.faultD.hurt2.A.storedB.collectedC.laidD.piled3.A.healthyB.completeC.effectiveD.painless4.A.observeB.skimC.watchD.examine5.A.UnexpectedlyB.Certainly smallC.UnfortunatelyD.Generally6.A.onceB.twiceC.three timesD.four times7.A.drillB.digC.cleanD.explore8.A.deliciousB.valuableC.beneficialD.meaningful9.A.whatB.howC.whetherD.when10.A.stick toB.attach toC.fix onD.keep to