单项选择题
A．have the lights turned on B．be rewarded with milk C．please their parents D．be praised
A．a basic human desire to understand and control the world B．the satisfaction of certain physiological needs C．their strong desire to solve complex problems D．a fundamental human urge to display their learned skills
A．until after 12 o'clock in the evening B．until early next morning C．all day and all night D．until 12 o'clock in the evening