A) Decrease the amplitudes of their jumps while increasing the variability of their jump periods
B) Decrease the amplitudes of their jumps while decreasing the variability of their jump periods
C) Increase the amplitudes of their jumps while increasing the variability of their jump periods
D) Increase the amplitudes of their jumps while decreasing the variability of their jump periods

A) People tilt back when a seen wall approaches, showing that the approaching wall signals falling forward
B) People tilt back when a seen wall approaches them, showing that the approaching wall signals falling backward
C) People tilt forward when a seen wall approaches them, showing that the approaching wall signals falling forward
D) People tilt forward when a seen wall approaches them, showing that the approaching wall signals falling backward

A) Motor development follows a rigid maturational progression
B) Motor development does not follow a rigid maturational progression
C) Developing a theory of motor development puts the theorist on a slippery slope that should be avoided
D) Developing a theory of motor development puts the theorist on a slippery slope that should not be avoided