Final answer:
In the happy baby pose, the shoulders should be relaxed and the shoulder blades flat on the floor, with the scapula able to move naturally, corresponding to option 'd', the scapula in an upward direction.
Step-by-step explanation:
In the happy baby pose, shoulders should be braced in such a way to support the body and maintain proper alignment. The provided details describe a hypothetical scenario rather than directly answering the question. However, it is known that when performing the happy baby pose, it is important to keep the shoulders relaxed and drawn down away from the ears, which helps to maintain a neutral spine position. Variations of the pose may include sitting or kneeling, and in some instances, participants might use their arm or elbow for support by placing it against their knee. Still, in the traditional happy baby pose, the focus is to ensure that the shoulder blades are flat on the floor and the scapulae are able to move naturally with the posture, which may correspond to option 'd' from the provided list, scapula in an upward direction.