At cut off, the Q point is at A. upper end of the load line B. middle of the load line C. lower end of the load line D. infinity E. None of the above

The correct answer is: C. lower end of the load line.

A load line is a graphical representation of the relationship between the collector current and the collector-emitter voltage of a transistor. The Q point is the point of intersection of the load line and the transistor’s transfer characteristics.

At cut off, the transistor is turned off and there is no collector current. This means that the Q point is at the lower end of the load line, where the collector current is zero.

Option A is incorrect

because the upper end of the load line corresponds to the maximum collector current. Option B is incorrect because the middle of the load line corresponds to the point where the collector current is half of the maximum value. Option D is incorrect because infinity is not a valid value for the collector current. Option E is incorrect because the Q point is always at a finite value.