she weighs about 2 kilograms at birth改错

she weighs about 2 kilograms at birth改错
she weighs about 2 kilograms at birth改错

she weighs about 2 kilograms at birth改错
这里应该用过去时比较合适.
She weighed about 2 kilograms at birth.

she weights about 2 kilograms at birth.

at后面加一个the 。 at the birth 表示出生，分娩的时候。这句话的意思是她出生的时候就已经有2公斤重了。

感觉没啥问题啊！