The neonate's big toe dorsiflexes and the other toes fan when the nurse gently strokes the sole of the foot. The nurse should interpret this positive finding as which of the following

A．Stepping reflex.

B．Plantar grasp.

C．Galant reflex.

D．Babinski sign.

美国心理学家耶克斯和多德森认为，最有利于提高学习效果的动机水平是()

A．低水平

B．高水平

C．中等水平

D．极高水平