【答案解析】Dear Mr. David,
I am writing to inform you of my decision about quitting from my current position of secretary in our company. I am regretful that it will bring about much inconvenience to you and our company.
Although having worked here for only three months, I unfortunately find that this job is not consistent with my expectation. For one thing, I have not had any opportunity to be responsible for any challenging task, which can"t satisfy my great ambition. For another, I have to say that my salary is far from supporting me to survive in this expensive city.
I apologize again for my resignation.