物体从静止开始做匀加速直线运动，已知第4s内与第2s内的位移之差是12m．则物体在第1s内的位移为____ m，在第5s内的平均速度为____ m/s．

阅读下列短文，从每小题的三个选项中选出最佳选项。

     Hello, I'm Linda. I have a garden. There are some plants and flowers in my garden. I like smelling flowers in it. Look at this small plant. It's a gift from my grandmother. It's for Children's Day. I like it very much. It is small and short. It has two small leaves. I water it every day. The plant grows and grows. Now it is big. It has more(更多) leaves. Now it has three pink flowers. They are beautiful. I like these beautiful flowers very much.

已知△ABC中，A：B：C=1：1：4，则a：b：c等于（　　）