1、It's my/a pleasure.和My pleasure.是回答别人说“谢谢”时使用,有“不用谢（这是我的荣幸）”的意思.
而With pleasure.是用于别人问你“能给我给帮助吗?（Could you help me…）”有“乐意帮你”的意思.
2、另it'a pleasure: - Thanks for your help. - It's a pleasure (没有关系)
it' my pleasure A: Thank you for your advice. B: it' my pleasure / It's a pleasure (没有关系)
a pleasure------- It is a pleasure to talk with you ----和你交谈是种乐趣
my pleasure： - Thanks. -My pleasure / it' my pleasure / It's a pleasure (没有关系)
with pleasure -----很乐意,很情愿 ------- -Can you do it for me ? -With pleasure.
with my pleasure (英语中应该没有这种表达)
