visa problem in china

The F Visa Explanation
The F visa, commonly referred to as the "business visa", is issued to an alien invited to China for: business; research; scientific, technological, and/or cultural exchange; short-term advanced study; or intern practice – for a period of not more than six months.
The F visa can be applied for at your local Chinese embassy or consular office. The following details the application requirements:
Types:
Single entry visa
Double entry visa
Multiple entry 6 Months
Multiple entry 1 Year
Multiple entry 2 Years
Single or Double Entry Visa Requirements:
(1) Current passport with at least 6 months validity
(2) Completed visa application form
(3) One recent passport-size photo
(4) Invitation letter from the host organization in China
6-Month or 1-Year Multiple Entry Visa Requirements:
(1) 6-month multiple entry: current passport with at least 6 months of validity; 1-year multiple entry: current passport with at least 1 year of validity
(2) Completed visa application form
(3) One recent passport-size photo
(4) One of the following requirements must be met:
Validity:
Validity refers to the amount of time a visa holder has to enter China from the issue date of the visa.
Visa Type: Validity:
Single entry visa 3 months
Double entry visa 6 months
Multiple entry 6 months 6 months
Multiple entry 1 year 1 year
Multiple entry 2 years 2 years
The above lists the usual amounts of time given to a visa holder to enter China depending on visa type. Applicants can request a longer validity period when applying. However, it is up to the local Chinese embassy or consular office whether or not to grant the request.
Duration of Stay:
Duration of stay refers to the amount of time a visa holder has to stay in China from the date he/she enters.
The usual duration of stay for all visa types (except the 2-year multiple entry visa) is 30 days. The usual duration of stay for the 2-year multiple entry visa is 90 days.
Applicants can request a longer duration of stay when applying – up to 6 months. However, it is up to the local Chinese embassy or consular office whether or not to grant the request.