4 cm
6 cm
8 cm
12 cm
Answer is Right!
Answer is Wrong!
The correct answer is B. 6 cm.
The waist of a stair is the horizontal distance between the two sides of the stair. It is an important dimension because it determines the amount of space that is available for people to walk on the stairs. The minimum waist for stairs spanning horizontally is 6 cm. This is to ensure that people have enough space to walk on the stairs without feeling cramped.
Option A is incorrect because 4 cm is not enough space for people to walk on the stairs comfortably. Option C is incorrect because 8 cm is not the minimum required waist for stairs spanning horizontally. Option D is incorrect because 12 cm is more than the minimum required waist for stairs spanning horizontally.