A：②④
B：③④
C：②③④
D：①②③
要求：1). 逻辑清楚，使用以下词汇： first, then, next, finally等。
2). 参考词汇：carrot, stones, hat, scarf
3). 不少于6句话。
We all know the air____us____．____makes the air dirty and it makes us unhealthy．Rubbish makes the land and water dirty．The dirty land and water makes us unhealthy and ____too．Trees make the____ ____and beautiful．Trees also give us delicious fruit and useful____．We should keep the air clean and ____throwing rubbish into rivers, lakes or seas．We should plant ____trees．
下列有关组成细胞的元素和化合物的叙述，正确的是（ ）
