执行以下代码后输出的结果是？ （ ）
d={1: ' monkey' , 2: ' panda' , 3: ' bird' , 4: ' fish' }
d[5]=' sheep'
del d[3]
d[3]=' dog'
print(d)
{1: ' monkey' , 2: ' panda' , 4: ' fish' , 5: ' sheep' , 3: ' cat' }
{1: ' monkey' , 2: ' panda' , 4: ' fish' , 5: ' sheep' , 3: ' dog' }
{1: ' monkey' , 2: ' panda' , 3: ' dog, 5: ' sheep' , 4: ' duck' }
{1: ' monkey' , 2: ' panda' , 3: ' cat' , 5: ' sheep' , 4: ' duck' }