Final answer:
To cultivate new growth and maintain the structure of locks grown from extensions, option B) interlocking is the recommended method as it incorporates and tightens new hair at the root of existing locks.
Step-by-step explanation:
When a braid with extensions grows away from the scalp and new growth needs to be cultivated to form a lock, the recommended method is B) Interlocking.
This technique involves taking the new growth and weaving it through the existing lock to tighten it at the root, helping maintain the lock's structure as the hair continues to grow. Palm rolling is a maintenance technique used for managing and smoothing the surface of locks. Two-strand twisting and backcombing are methods used for initially creating locks, not for maintaining new growth at the scalp.