题目

完形填空 An old man lived in a nice house with a large garden. He took care of his flowers all the time, watering and fertilizing them. One day a young man went by the garden. He looked at the beautiful flowers, imagining how happy he could be  1   he lived in such a beautiful place. Then, suddenly he found the old gardener was  2   . He was very surprised about this and asked, You can't see these flowers.Why are you busy taking care of them every day? The old man smiled and said I can tell you four  3   . First, I was a gardener when I was young, and I really like this 玉米是我国重要的粮食作物。下面关于玉米的叙述，正确的是（　　）A.玉米是单子叶植物，一粒玉米是由一个胚珠发育来的B.在新鲜的玉米种子剖面上滴加碘液，变蓝的部分是胚C.种子萌发时，胚根首先突破种皮发育成根并且子叶出土D.玉米为雌雄同株植物，借助风力完成异花传粉