There is an "auxiliary verb" error in your first sentence. Since you are talking about "the past" you need to change it to something like this first: A: Yesterday Mark told me you "were" thinking of quitting your job, why didn't you tell me? For the second part. You need to know the difference between Past Simple and Present Perfect. Past Simple (or Simple Past) means that the action you are talking about is simply finished. It has no result/effect in the present. Present Perfect means that the action either finished or didn't finish. But it has effects in the present. For example: - I've tried many times to tell you (it means I tried in the past and didn't finish trying it. I still want to try again - in the present) - I tried many times to tell you (it means I tried in the past and now its done. I'm not trying again now.) The last sentences: - I have built up some courage (it means I started building up my courage but it's still not finished) - I built up some courage (it means I did it in the past but now its finished) - You have been busy and couldn't hear me out (you were busy then and you are busy now - not finished) - You were busy and couldn't hear me out (you were busy in the past when I asked you at that specific time - finished) So let me get to your answer. The correct answer is below: A: Yesterday Mark told me you "were" thinking of quitting your job, why didn't you tell me? B=I really wanted to I swear, "I've tried" many times to tell you but everytime I "built up" some courage you "were" busy and couldn't hear me out." * You are still trying today, its not finished, so the first choice is "Present Perfect". * You built up your courage in the past at those specific times so it should be "Simple Past". * You were busy at those specific times and it finished. Hope this helps ;)