执⾏下⾯Python代码后 ，输出的结果是？ ( )
keys = [ 'a ', 'b ']
values = [[1], (2,)]
d = {k: v for k, v in zip(keys, values)}
d['a '].append(3)
print(d['a '])
[1]
(2,)
[1, 3]
报错