[单选题]集合members,包含数据[{name:"zs",hobby:["唱歌","跳舞","打游戏"]},{name:"ls",hobby:["跳舞","唱歌"]}]),查询拥有3个爱好的文档 ( ) A. db.members.find({hobby:{$count:3}}) B. db.members.find({hobby:{$len:3}}) C. db.members.find({hobby:{$size:3}}) D. db.members.find({hobby:{$length:3}})