Food coloring (optional).

食用色素(可选)。

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Full Time Junior Golf & Academic Program: RMB 115,000/Semester inclusive of golf instruction and golf game. Limousine service, canteen food, schools and dorms are optional.

全日制高尔夫和文化班：每学期115，000元人民币年包括学球打球费用。豪华轿车接送服务、学校、饭堂伙食和住宿项目可根据个人需要选择。

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But such optional testing of a medical food is usually far less stringent than the regulatory hurdles drug makers face when trying to bring a new treatment to the market.

WSJ: 'Medical Foods' and Supplements for Brain Health Advance

Also, the poor quality of the food and wine served at the optional Czech Dinner and folk show excursion did not reflect the quality of that served on the cruise itself.

FORBES: Watching History Unfold: A Cruise Expert Takes His First River Cruise

One third said that free food at meetings would prompt them to attend optional meetings.

FORBES: Motivation By Mouth: Does Free Food Make For A Happier Workplace?