Refer the given figure. Which of the following describes the operation of the circuit?

• A. A LOW input turns Q1 and Q3 on; Q2 and Q4 are off.
• B. A LOW input turns Q1 and Q4 off; Q2 and Q3 are on.
• C. A HIGH input turns Q1, Q2, and Q3 off, and Q4 is on.
• D. A HIGH input turns Q1, Q2, and Q4 on; Q3 is off.