有关机器学习分类算法的Precision和Recall，以下定义中正确的是（假定tp = true positive, tn = true negative, fp = false positive, fn = false negative）（ ）

A、Precision=tp/(tp+fp),Recall=tp/(tp+fn)
B、Precision=tp/(tn+fp),Recall=tp/(tp+fn)
C、Precision=tp/(tn+fn),Recall=tp/(tp+fp)
D、Precision=tp/(tp+fp),Recall=tp/(tn+fn)