如果3  5是3和5的倍数，那么横线上可能是（   ）。

细读课文深感悟。

植物学家修建花钟的做法真妙，妙在哪儿？你认为下列说法哪个有道理，把序号写在括号里。(  )

    Bird lovers know that a good place to go bird-watching is Guandu Nature Park. As many as 220 kinds of birds come to this park every year. Since the park offers birds lots of food to eat and places to build their nests, it has become a paradise（天堂）for birds.

    Guandu Nature Park is also a great outdoor classroom. The park's Nature Center provides guided tours to the public. During the tour, visitors can learn about the environment. So, if you want to have a fun and educational weekend, come to Guandu Nature Park. Get away from city life and head into nature.