Correct answer: (A) Device parasitic capacitances act as open circuits; coupling and bypass capacitances act as short circuits.
Explanation
The mid-band lies above the low-frequency corner frequencies introduced by large coupling and bypass capacitors. Their reactances are then small, so they are treated as shorts.
It also lies below the high-frequency corner frequencies associated with small device parasitic capacitances. Their reactances remain large and are treated as opens. Thus the appropriate approximation is **A**.
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