以下程序的运行结果是？（ ）
a={"name":"jt","age":29,"class":5}
a["age"]=15
a["school"]="派森社"
print("age:",a["age"])
print("school:",a["school"])
age: 29 school: 派森社
age: 15
age: 15 school: 派森社
school: 派森社