A:CO2→CO
B:CO2→CaCO3
C:CO→CO2
D:CO→H2CO3
如图,四棱锥P﹣ABCD中,PA⊥底面ABCD,AB⊥AD,AC⊥CD,∠ABC=60°,PA=AB=BC,
E是PC的中点.求证:
(Ⅰ)CD⊥AE;
(Ⅱ)PD⊥平面ABE.
由欧洲国家组成,对世界影响巨大的政治、经济实体是:( )
工程和建筑都是文明的载体。我国现存规模最大、最完整的古建筑群是( )
In his first class, the Chinese teacher tried to ________ to the students that reading is one of life's greatest pleasures.