The second volume of Senior Two is divided into two versions, A and B, mainly because of the different solutions of solid geometry in the second volume of Senior Two. Version A is a traditional geometric method that uses axiomatic theorem as an auxiliary line to solve solid geometry problems. Version B is a new content, that is, following the knowledge of plane vector in Volume One, using the method and concept of space vector to solve solid geometric problems, and algebraic calculation to solve geometric problems. The standard answer to the big question of solid geometry in the college entrance examination will include the solutions of these two methods. So you can cope with the college entrance examination by learning any method. The B version is mainly used in some big cities or areas with curriculum reform, such as some schools in Beijing.