1） 未及时回信的原因；
2） 你假期的打算（如做兼职、旅行、做志愿者等）；
3） 希望有时间来中国玩。
注意：
1）字数：120左右；
2）可适当增加细节，以使行文连贯。
Dear Jack,
……
Yours truly,
To begin with, please accept my sincere apology for not replying to your last letter in time. During those days, I'd been busy preparing for the final exam which was very important to me.
Now the winter vacation is approaching, during
