Qual das alternativas expressa o uso correto do present perfec...

Qual das alternativas expressa o uso correto do present perfect? *20 pontos
A) To talk about a completed past action at a non- specific time. The action is finished. You don't remeber when it happen.
B) To talk about a incompleted past action at a non-specific time. The action isn't finished.
C) With the words "since" and "for" to talk about a something that began in the past and continues to now.