My pleasure 与 It is a pleasure有什么区别?what a shame?什么意思?

It is a pleasure=It is my pleasure;
my pleasure 其实就是it is my pleasure的简称.
所以my pleasure 和 it is a pleasure是一样的.
What a shame.的意思是真糟糕、真不争气,用于表述懊恼的情绪!