下面代码的输出结果是？（ ）
dict1 = {1: 10, 2: 20, 3: 30} dict2 = {2: 40, 4: 50} dict1.update(dict2) print(dict1)
{1: 10, 2: 40, 3: 30, 4: 50}
{2: 40, 4: 50}
报错