一个湖泊被DDT污染，在湖泊中有一条食物链：藻类→水蚤→鱼→鱼鹰．由此，可推定体内DDT含量最多和最少的生物分别是（　　）

据此分析，若用F₁（黑鲤）与红鲤测交，子代中不同性状的数量比是（  ）

完形填空

通读下面的短文，从A、B、C三个选项中，选出一个最佳选项填空,使短文意思通顺、结构完整。

      Are there aliens? In the movie Home there1. The Boov are aliens. But their enemies ruined their planet. 2the Boov have to find a new planet. They choose to go to 3and drive people away.

      Earth is a good place. The Boov are4there. They have a party to celebrate. But a Boov named Oh makes a big 5. He asks everyone to come to their party, including their enemies. Other Boov think Oh is 6 spy(间谍). Oh 7run away. He meets Tip, the last8on Earth. Tip is smart. The Boov can't catch her.

      Both Oh and Tip are on the run. They become friends and go on adventures. On the way, the9 change each other's world. And they get to understand the true meaning of “10”.