这些微小的尘埃颗粒在空气中是不可见的。

These tiny dust particles are ___invisible in the air.

这种化学物质的危害通常是肉眼不可见的。

The dangers of this chemical are often ___invisible to the naked eye.

隐私选项在默认设置下是隐藏的。

The privacy options are ___invisible in the default settings.