在Car类中自定义speed方法，输出：the speed is 60km/hClass Car(): def __init__(self): self.name='baoma'代码正确的是（）
选项：

A:def speed(): print('the speed is 60km/h')
B:def speed(self): print('the speed is 60km/h')
C:def speed(self) print('the speed is 60km/h')
D:def speed() print('the speed is 60km/h')