快!Don't mind too much about ---- mistakes. They are just ---

B
A is incorrect because there must be an article before "natural part of learning"
C is incorrect because we do not talking about specific mistakes.我们不是要指定的说那些错误.
D is incorrect and the reason is the same as C.
整句的汉语是 不要太在意错误.他们是学习过程中自然发生的.