**Core Concept**
The development of the temporomandibular joint (T.M.J) is a complex process involving multiple embryological stages. The T.M.J is formed by the fusion of the mandibular and maxillary processes, which eventually give rise to the articular disc and the condyle of the mandible. Understanding the timing of T.M.J development is crucial for dental and maxillofacial surgeons to diagnose and treat various disorders affecting the joint.

**Why the Correct Answer is Right**
The correct answer is 10 weeks, which corresponds to the stage of mandibular development when the articular disc and the condyle of the mandible begin to form. At this stage, the maxillary and mandibular processes start to differentiate and grow towards each other, eventually forming the T.M.J. The development of the T.M.J is a dynamic process that involves the coordinated growth of the mandible, maxilla, and the articular disc.

**Why Each Wrong Option is Incorrect**
**Option A:** 6 weeks is too early for T.M.J development, as at this stage, the mandibular and maxillary processes are still in the process of differentiation and have not yet formed the articular disc and condyle.
**Option C:** 18 weeks is too late for T.M.J development, as by this stage, the articular disc and condyle have already formed and the joint is well-established.
**Option D:** 16 weeks is also incorrect, as it is slightly later than the correct answer and the T.M.J development is already well underway by this stage.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the T.M.J develops from the fusion of the mandibular and maxillary processes, and any disruptions in this process can lead to various disorders affecting the joint, such as temporomandibular joint dysfunction (TMD).

**✓ Correct Answer: B. 10 weeks**