B

    A small, white envelope(信封) stuck among the branches of our Christmas tree and it has been there for the past ten years or so.

    It all began because my husband Justin hated Christmas—oh, not the true meaning of Christmas. Overspending was one thing, but compared to the difficult experience of choosing gifts—running around at the last minute to get a tie for Uncle Harry and a pair of gloves for Grandma…… spending money is nothing. I felt too tired to think of any special gifts.

    Knowing Justin felt the same way, I decided one year not to buy the usual shirts, sweaters, ties and so on. I reached for something special just for Justin. The inspiration came in an unusual way.

    Our son Kevin, who was 12 that year, was wrestling(摔跤) at the junior level at the school he attended; and shortly before Christmas, there was a match against a team sponsored(赞助) by an inner-city church. These youngsters, dressed in such worn out shoes that shoe strings seemed to be the only thing holding them together, while our boys were in their blue and gold uniforms and new wrestling shoes.

    As the match began, I was shocked to see that the other team were wrestling without wearing helmets(头盔) to protect their ears. Well, our boys ended up defeating them. We took every weight class.

    Justin, seated beside me, shook his head sadly, "I wish just one of them could have won," he said. "They have a lot of potential(潜力), but losing like this could take the heart out of them." Justin loved kids-all kids, and he knew them, having coached little league football and baseball. That's when the idea for his present came. That afternoon, I went to a local sporting goods store and bought different kinds of wrestling helmets and shoes. I sent them to inner-city church without leaving my name.

    On Christmas Eve, I placed the envelope on the tree, the note inside telling Justin what I had done and that was his gift from me. His smile was the brightest thing about Christmas that year and since then the envelope has become the highlight of our Christmas.

某动物的基因型为AaBb．下图甲表示该动物产生的一个精细胞中有关基因在染色体上的分布，乙和丙是该精细胞形成过程中的细胞分裂图．据图回答：

下面是小红的“物理笔记”部分摘录，其中不正确的是（　　）