According to the passage, humans mechanism of forgetting is under threat in the digital age because______.
A.the mechanism of forgetting is no longer with us in this age
B.dealing with Facebook messages, e-mails, tweets, etc. keeps us occupied
C.advanced digital tools help us decide what to forget
D.a comprehensive digital memory constantly reminds us of the past
请帮忙给出正确答案和分析,谢谢!