1. **State the problem:** Among the proposed answers, identify the correct one for the first question: "The complement angle of 40° is:" 2. **Recall the definition:** The complement of an angle $\theta$ is $90^\circ - \theta$. 3. **Apply the formula:** $$\text{Complement of } 40^\circ = 90^\circ - 40^\circ = 50^\circ$$ 4. **Check the proposed answers:** - A: 50° - B: 150° - C: 140° 5. **Conclusion:** The correct complement angle of 40° is 50°, which corresponds to answer A. Final answer: **50°** (Option A)