What is the missing line of code?

>>> info = {3:10, 4:23, 7:10, 11:31}
>>>_____
>>> info
{3: 10, 4: 23, 7: 10, 11: 31, 15: 23}

info.append({15:23})

info.update({15:23})

info.add{15:23})

info.insert({15:23})