我昨天无法通过电话联系到她。

I was ___unable ___to reach her by phone yesterday.

她太紧张了，以至于无法回答问题。

She was so nervous that she was ___unable ___to answer the question.

没有签证，你将无法进入这个国家。

Without a visa, you will be ___unable ___to enter the country.