A:owes it to; what
B:owes to; that
C:owes them to; that
D:owes it to; that
Smith 夫妇的孩子Alex 已经一个星期没有回家了,他的父母很为他着急。请您为他们写一则寻人启事。
Name
Alex
Age
14
Appearance
Tall, of medium build, short hair,big eyes, a small nose,a big mouth, wear glasses
Clothes
White shirt, blue pants, black shoes
Telephone
602—2615
Have you seen a girl anywhere?
如上图所示,纸筒A的一端蒙了一层半透明纸,纸筒B的一端嵌了一个凸透镜,两纸筒套在一起组成了一个模型照相机.为了在A端得到清晰的像,要调整AB间的距离,这时 ( )