Final answer:
Normal dry hair is capable of being stretched to about 20-30% of its length before breaking, as hair has some natural elasticity which allows for styling.
Step-by-step explanation:
Normal dry hair has the ability to stretch and is somewhat elastic. When stretched, normal dry hair can typically extend to about 20-30% of its original length before breaking. Considering the options given and understanding the normal elasticity of hair, we can determine that the final answer falls within the range specified in option A (20-30%). Stretching beyond this range, such as 50-70% or even more, would likely result in hair damage or breaking, especially when dry. This elasticity allows for some manipulation of hair through styling without causing immediate damage, but care should be taken not to overstretch.