回複：一個非常複雜的問題，跪問各位大俠，感激不盡！！！

Usually, US visa allows to have 3 months period to enter the US after got Visa. Once you got visa and it's up to you for when you want to come to US. In case that INS officer asked why you come alone not with tour group. Just tell them you have emergency by the time of about departure for US. SO you decide come this time. Often they won't ask you that much since you have Visa and assume you can go back to England freely.