Final answer:
The most challenging activity from a motor-control standpoint would be standing on a foam board while making a sandwich. This activity tests a person's ability to maintain balance and coordination while performing fine motor tasks.
Step-by-step explanation:
The most challenging activity from a motor-control standpoint would be B. Have your client stand on a foam board while making a sandwich.
This activity requires not only walking, but also balance and coordination while performing manual dexterity tasks. Standing on a foam board adds an additional challenge as it is an unstable surface that tests the person's ability to maintain balance.
In comparison, A. Have your client walk on a moving sidewalk may require some adjustments to maintain balance, but it does not involve the same level of fine motor control as the foam board activity. C. Have your client walk on the sidewalk is a common activity that does not pose as much challenge in terms of motor control. D. Have your client put away dishes in the sink primarily involves manual dexterity and does not require significant balance or coordination.