Z+ moves the end of the arm straight up.

• A. Z+
• B. X+
• C. Y-
• D. Z-

Answer: (A)

Movement along a robot’s axes is defined by a coordinate system where each axis has a positive and negative direction. The Z axis represents the vertical dimension, so increasing Z moves things upward. Saying that Z+ moves the end of the arm straight up matches this: you’re raising the end effector by increasing the Z coordinate while keeping X and Y constant.

If you used X+ or Y-, you’d be moving along a horizontal axis instead, not up or down. Z- would lower the end effector. So the statement about Z+ producing an upward movement correctly describes the vertical, positive direction along the Z axis.