How do we know the weather? We learn it on the radio and TV every day. Different countries have different weather. For example, the weather in Australia is different from that in China. Because the seasons in Australia are the opposite. Its summer is from December to February. But in our country, it's winter this time. And its winter is in June, July and August. So when it's spring in China, it's autumn in Australia. Isn't it interesting?

已知：I. （R或R´可以是烃基或H原子）。

II．反应①、反应②、反应⑤的原子利用率均为100％。

请回答下列问题：

已知四棱柱ABCD﹣A₁B₁C₁D₁的底面ABCD是边长为2的菱形，AA₁=2$\sqrt{3}$，BD⊥A₁A，∠BAD=∠A₁AC=60°，点M是棱AA₁的中点．

（Ⅰ）求证：A₁C∥平面BMD；

（Ⅱ）求点C₁到平面BDD₁B₁的距离．