你填得很对!（is也行,但不能填was)
weigh ( 动词)有…重;重...
It weighs nearly 27 kilos (about 65 pounds)... 它重近27千克(约65磅).我说的was是when he was born那前面也用过去时，但前面是the dog，而不是a dog.填was/ weighed哦，好吧，谢谢！那The dog weighs about 8 kilos when he is born.可以吗The dog weighed about 8 kilos when he was born.这条狗出生时约8公斤。（用过去时）A dog weighs about 8 kilos when he is born.Dogs weigh about 8 kilos when they are born狗出生时约8公斤。表示泛指用不定冠词+单数名词或复数名词（前不加冠词）