It's Sunday afternoon. Michael's family have a picnic under (在……下面) a big tree. The woman in a blue T-shirt and white pants is Michael's mother. ⑴She is thirty-two. She is a teacher in No. 2 high School. She is cooking now. The man with a guitar is Michael's father. He is thirty-four years old. ⑵He teaches in the same school as Michael's mother. He is a teacher. Michael's little sister likes singing, but she isn't singing now. ⑶“为什么不和我一起去放风筝呢？”Michael问他的小妹妹。⑷Then she flies a kite with her brother. What a happy family!

Mike __________ live in London, but now he works in China.

课内阅读《学会看病》。

        孩子，不要埋怨我在你生病时的冷漠。总有一天，你要离我远去，独自面对生活。我预先能帮助你的，就是向你口授一张路线图，它也许不那么准确，但聊胜于无。

如图，在Rt△ABC中，∠ACB=90°，AC=3，BC=4，过点B作射线BB₁∥AC．动点D从点A出发沿射线AC方向以每秒5个单位的速度运动，同时动点E从点C沿射线AC方向以每秒3个单位的速度运动．过点D作DH⊥AB于H，过点E作EF⊥AC交射线BB₁于F，G是EF中点，连接DG．设点D运动的时间为t秒．

当t为何值时，AD=AB，并求出此时DE的长度；