I'm at a loss as to how to explain the error. [=I don't know how to explain the error]我不知道如何解释这个错误。

There is disagreement as to the causes of the fire.对于火灾的原因，目前存在不同看法。

I remained uncertain as to the value of his suggestions.他的这些建议价值如何，我有些拿不准。

The eggs are graded as to size and color.这些鸡蛋是按照大小和颜色分等级的。