在观察光的干涉现象的实验中，将两刀片合在一起，在涂有墨汁的玻璃片上划出不同间隙的双缝；按图所示的方法，让激光束通过自制的双缝．

①保持缝到光屏的距离不变，换用不同间隙的双缝，双缝的间隙越小，屏上明暗相间的条纹间距____（选填“越大”或“越小”）；

②在狭缝间的距离和狭缝与屏的距离都不变的条件下，用 不同颜色的光做实验，发现用蓝色光做实验时屏上明暗相间的条纹间距比用红色光做实验时____（选填“大”或“小”）．

我国黄土高原上的传统民居有

B

    Fraser is four years old. He has autism(自闭症). He lives in his own world. Everything is very difficult to him. He doesn't want to play with other children. He doesn't want to say any words to others. His parents are worried about him.

    Then Billy, a cat, comes. It helps Fraser go out of his world.

When Billy sees Fraser, it runs to him quickly. It sits beside Fraser with its paws on Fraser's legs. They seem to be old friends. Fraser says, "This is our cat. He can come to live with us." "I know our life changes," says Fraser's mother.

    Billy stays with Fraser all the time. They play together, listen to the story together and sleep together. When Fraser walks in the garden, Billy is never far away. When Fraser is unhappy, it always lies beside him.

    It seems crazy. But Billy is like Fraser's angel. Fraser changes a lot. The doctor says he is getting better. He doesn't have to see the doctor now.