ANS:C - unacceptable

In this world of semiconductor, anything above VL (max) and below VH (min) is unacceptable, because that is called state of uncertainty.

It has to do with noise margins and fabrication defects. VL (max) is acceptable noise margin for low state, VH (min) is acceptable noise margin for high state.

Actual voltages may differ from implementations to designs and fabrication methods.