Sally is looking at a big ship.为什么要用at?

Sally is looking at a big ship.改否定句 Sally is looking at a big ship.改否定句 Sally is looking at a big ship.为什么要用at? sally is looking at the the plane (和朋友一起） Mr Jones and his wife and looking at them,Sally is looking at a big ship,句子中的各词性是? Is Sally good at ___________? Is Sally good at schoolwork? 英语语法请教sally is looking at a big ship莎莉 is 正在看 at 一只大船这里的is 和 at 求教 九年级英语5单元单项选择sally is good looking and she enjoy looking at in the mirror.A.it B.her C .she D.herself where is Sally? Tim is looking at an aeroplane. Here is another photograph.句子中的be（is）在句子中的作用是什么? is Sally at school?is 前面要加什么? Bob!Is this your dictionary?No,it isn't.Ask Sally.She is looking for____ Bob!Is this your dictionary?No,it isn't.Ask Sally.She is looking for____ Sally is good at ___(play)the violin. Sally is at school.改为一般疑问句和否定句 Helen -----a good job.A.is looking for B.is looking after C.is looking at D.is looking up She is looking at her photos. Tom is looking at the backboard.祈使句