Step 1: Understanding the question.
The minimum vertical distance of a dwelling unit from high voltage electric lines is a safety standard aimed at reducing the risk of accidents and electrocution. These guidelines are issued by safety authorities to ensure public safety around power lines.
Step 2: Analyzing the options.
(A) 3.7: Correct — According to safety regulations, the minimum vertical distance from high voltage electric lines to any dwelling is typically 3.7 meters.
(B) 2.5: This distance is insufficient for high voltage power lines.
(C) 1.2: This distance is too small and does not meet the safety standards for high voltage electric lines.
(D) 4.2: This is higher than the required minimum, though it may be applicable in certain specific scenarios, the correct minimum is typically 3.7 meters.
Step 3: Conclusion.
The correct answer is (A) 3.7, which is the minimum vertical distance for safety around high voltage power lines.