A.http：//hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/core-default.xml
B.http：//hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-hdfs/hdfs-default.xml
C.http：//hadoop.apache.org/docs/current/hadoop-mapreduce-client/hadoop-mapreduce-client-core/mapred-default.xml
D.http：//hadoop.apache.org/docs/current/hadoop-yarn/hadoop-yarn-common/yarn-default.xml