题目

阅读理解Have you ever heard about Black Friday and Cyber Monday? Surely, they are all about finding the best deals on holiday gifts for yourself and family members. And have you heard about Giving Tuesday? Here is something about it.GivingTuesday is celebrated on the Tuesday after Thanksgiving every year, which encourages people to help those in need by raising money-or doing good in their local community. GivingTuesday was started in 2012 by New York City Nonprofit and the United Nations Foundation. :Unlike Black Friday, GivingTuesday serves a more selfless purpose. In its first year, the一个杂交组合的后代，（F1）呈3：1的性状的分离比，这个杂交组合是（   ）A．DdTt´DdTtB．DD´DDC．Dd´ddD．DDTt´ddTt