题目

This book is said to be a special one, which______ many events not found in other history books.    A. writes              B. covers         C. deals                 D. refers 答案：B根据下列证明过程填空： 如图，BD⊥AC，EF⊥AC，D、F分别为垂足，且∠1=∠4，求证：∠ADG=∠C 证明：∵BD⊥AC，EF⊥AC ∴∠2=∠3=90° ∴BD∥EF ( ) ∴∠4=_____ ( ) ∵∠1=∠4 ∴∠1=_____ ∴DG∥BC ( ) ∴∠ADG=∠C( )