1.此题因为上句提到了“我们明天要英语大考”这件事,所以用Good luck!“（祝你们)好运!”最合适.
而Best wishes to you!意思是“给你最好的祝愿/祝福!”是宽泛的祝福用语,没有明确的针对对象.也就是说不管对方又没有什么事,你都可以这么说.
2.此题考查定语从句关系代词的用法和区别.
1）被该定语从句所修饰的名词短语是the children,在语法上被称为先行词.
而关系代词who等于/代替先行词the children,在后面的定语从句中充当句子的主语,所以用主格代词who.
即完整的定语从句为：who lost their parents in the earthquake = the children lost their parents in the earthquake
2）而表宾格的关系代词whom在定语从句中必须充当宾语才可以用.
如：We should show our love to the children whom their parents have left.
即定语从句whom their parents have left = their parents have left whom = their parents have left the children
此时,whom也等于先行词the children,在定语从句中做谓语动词left的宾语.
3）whose等于/代替先行词的所有格形式,即“先行词's”.
如：We should show our love to the children whose parents died in the earthquake.
其中：whose parents died in the earthquake = the children's parents died in the earthquake
此时关系代词whose = the children's.
4）至于楼主说的whom是show的宾格,的确有点无厘头.
show的宾语是主句中的our love或the children,和定语从句的关系代词没有任何关系.