洋葱鳞片叶内表皮细胞具有，而人体细胞中没有的结构是（　　）

在同一条直线上的P、Q、R三点，一物体从P点静止开始做匀加速直线运动，经过Q点的速度为v，到R点的速度为3v，则PQ∶QR等于(　 　)

根据中文意思填空，完成短文，并注意单词的正确拼写形式。(每空一词)

    Do you enjoy eat nuts? Have you ever tired Chinese torreya nuts(香榧)? Zhuji is ____（广泛地） known for this special kind of nuts. Most of the Chinese torreya trees are grown in the ____（东部） of Zhuji. Every autumn, the nuts are picked by the ____ （当地的） people and then sent for ____ （加工）. Not everyone gets the ____（秘诀）of frying(炒制) the nuts. Only the experienced workers can make it. People in Zhuji take ____（骄傲）in the Chinese torreya nuts, and the nuts are usually ____（放置）out to treat ____( 亲属 ) and friends. Nowadays, more and more people fall in love with the nuts. And it ____ (创造) good business for Zhuji. What a great ____（影响）the Chinese torreya nuts have on Zhuji!

（Ⅰ）证明：CD⊥平面PAD；

（Ⅱ）若二面角P﹣CD﹣A的大小为45°，求几何体C﹣PBE的体积．