S. guidelines, issued in 1997, call for 200 international units from birth through age 50;400 IUs from 51 through age 70 and 600 IUs from 71 on.是什么意思_S. guidelines, issued in 1997, call for 200 international units from birth through age 50;400 IUs from 51 through age 70 and 600 IUs from 71 on.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句