如图，在平行四边形ABCD中，点E是BC的中点，∠BOE=30°，OD=2，cos∠ADB=____ ．则CD=____ 

（I）证明：CD⊥平面PBD；

（II）求二面角A﹣PD﹣C的余弦值．

下列命题：①在$△ABC$中，若A>B，则sinA>sinB；②已知$\overrightarrow{AB}=\left(3,4\right),\overrightarrow{CD}=\left(-2,-1\right)$，则$\overrightarrow{AB}$在$\overrightarrow{CD}$上的投影为-2；③已知$P:\exists x\in R,\cos x=1$，$q:\forall x\in R,x^2-x+1>0$，则“$p\wedge \neg q$”为假命题．其中真命题的个数为（ ）

根据短文理解，从A、B、C、D四个选项中选择最佳答案填空。

    July 20th, 1969 was an important day. Two Americans 1 on the moon. Their 2 were Armstrong and Aldrin. They went there in a 3. Its name was ApolloⅡ.

    ApolloⅡ left the earth 4 July 16th and went three hundred and eighty-five thousand kilometers. It 5 the two Americans three days to get there. On July 20^th, the spaceship landed in the Sea of Tranquility (安静的世界). Armstrong 6 stepped onto (踏上) the moon. The two men walked on the surface of it. They 7 up some rocks and put them in the spaceship. They jumped up and down. They were 8 after their walk. So they had a rest.

    On July 21th, ApolloⅡleft the moon and 9 to the earth. Three days 10 it came down in the Pacific Ocean (太平洋). A ship took the men to America.

中央纪委网站公布2015年1月全国查处八项规定情况，全国共查处违反中央八项规定精神问题1 650件，处理人数2133人，给予党纪政纪处分1406人。网络反腐彰显了强大威力，网络反腐热潮正改变着中国的反腐格局。网络反腐（    ）

①是我国社会主义民主最为广泛而深刻的实践

②已成为新形势下反腐倡廉的主要形式

③是通过社会与公民的监督促进廉政建设

④拓宽了人民民主对权力的制约和监督的渠道