B
注意中间的逗号,后半句是省略形式,相当于.The old man walked in the street,The old man ______.如果用A,则需要成为Some body BE followed by SOME ONE;选C（题中第二排的B）的话前后句时态不对；选D的话被动语句少Be动词,B答案正确,全句可还原为：The old man walked in the street,The old man followed his son .