ANS:B - free-running multivibrator

An astable multivibrator is also known as a FREE-RUNNING MULTIVIBRATOR. It is called free-running because it alternates between two different output voltage levels during the time it is on.

The output remains at each voltage level for a definite period of time. If you looked at this output on an oscilloscope, you would see continuous square or rectangular waveforms. The astable multivibrator has two outputs, but NO inputs.