写作。根据中文提示，写出内容完整、意思连贯、符合逻辑、不少于50词的短文。

       下面是一位美国中学生的来信。假设你是王英，请你写一封回信，解答他来信中提出的问题。（信的开头及结尾均已给出，不计入总词数。）

Dear Wang Ying,

        How are you? Summer holiday is coming soon. I'm going to the seaside for my holiday. But I don't like

to go there with my parents. I don't get on well with them because they are always trying to teach me. Do you

have the same problem? What about parents? How can we get on well with our parents?

        Hope to hear from you soon. 

                                                                                                                                           Yours, 

                                                                                                                                      David Smith  

Dear David,

        Thank you for your letter. I'm very well, thank you.

        For my summer holiday,                                                                                                                  

        Hope to hear from you again.

                                                                                                                                           Yours,

                                                                                                                                        Wang Ying      

人体缺乏维生素C（简写Vc）会患坏血病。下图所示为某种“维生素C”说明书的一部分，请回答：

（1）Vc中C、H、O三种元素的质量比是    。

（2）若正常成人每天对Vc的最低需要量为60mg。

①当这些Vc完全来自右图的“维生素C”时，则每次服用“维生素C”至少           片；

②当这些Vc完全来自某种新鲜蔬菜（每1000g这种蔬菜含Vc120mg）时，每天至少应食用这种蔬菜  g。

③维生素C又名抗坏血酸，其水溶液能使紫色石蕊试液变    色。