never mind 和 take your time

never mind 和 take your time
这两个是不是都有没关系的意思?具体来说有什么区别?
看下这两个例题
1.------I am afraid I can't return the book to you before Friday.
-------______.
A Don't be afaid B Be careful C Not at all D Take your time
这题里C和D选谁?
2.-----Do you mind do I owe you for lunch?
------_____.It's noting.
A Never mind B Forget it C With pleasure D That's right.
这题为什么不选A?