根据汉语提示完成句子
⑴____ （汉堡包） are not good for us.
⑵Heroes like eating mangoes, potatoes and ____  (西红柿) with knives.
⑶She likes dancing very much and she____  (需要) a lot of energy to dance.
⑷He always gets a lot of ____   (礼物) at Spring Festival.
⑸All careful persons ____  (从不) carry noodles in this way.
⑹Did they have a party to celebrate Halloween on____  (十月) 31^st?
⑺Her lifestyle is not____ （健康）.
⑻Millie knows Simon likes____  （收集）stamps.
⑼Oh, they don't fit well. Can I see ____ （另外的） pair?
⑽Most of the children in poor____ （地区） never listen to CDs.

如图所示为用某种透明材料制成的一块柱形棱镜的横截面图．圆弧CD是半径为R的四分之一圆周，圆心为O．光线从AB面上的M点入射，入射角i=60°，光进入棱镜后恰好在BC面上的O点发生全反射，然后由CD面射出．已知OB段的长度为l=6cm，真空中的光速c=3.0×10⁸m/s．求：

（Ⅰ）透明材料的折射率n；

（Ⅱ）光从M点传播到O点所用的时间t．