那个地区的路况有点不确定。

The road conditions in that area are a bit of ___an ___unknown ___quantity.

如上所述，激光束甚至对其发明者来说都是一个未知数。

As mentioned above, the laser beam was ___an ___unknown ___quantity even to its inventor.

他对这个消息的反应仍然是个未知数。

His reaction to the news is still ___an ___unknown ___quantity.