Final answer:
The blow-dryer attachment used to stretch and soften textured hair is known as a comb nozzle or pick attachment. It helps to straighten hair while drying by using long teeth to comb and stretch the hair strands, which loosens the curl pattern.
Step-by-step explanation:
The blow-dryer attachment that stretches and softens textured hair and loosens the curl pattern is known as a diffuser. However, in the context of straightening textured hair, the attachment that is specifically designed for stretching and loosening curls is called a comb nozzle or pick attachment. This attachment is typically used on a blow dryer to straighten hair while drying. It has long teeth that comb through the hair, stretching the strands out as they dry, which in turn softens the natural texture and loosens the curl pattern. This is a common tool used in hair styling, especially for individuals with curly or textured hair who want to achieve a straighter style without using direct heat such as flat irons.