单选题：以下哪一项将判断机器龟的画笔是否抬起，如果抬起，则命令机器龟把画笔放下？

以下哪一项将判断机器龟的画笔是否抬起，如果抬起，则命令机器龟把画笔放下？

@[C](2)

A. if turtle.isup():
turtle.isdown()
B. if turtle.isdown
turtle.penup()
C. if not(turtle.isdown()):
turtle.pendown()
D. if not(turtle.penup())
turtle.penup()



A.if turtle.isup():
turtle.isdown()
B.if turtle.isdown
turtle.penup()
C.if not(turtle.isdown()):
turtle.pendown()
D.if not(turtle.penup())
turtle.penup()


答案：C