If the physics textbook is placed on the horizontal table and the pencil case is placed on the physics textbook, then () A. The gravity of physics textbook and the supporting force of desktop on physics textbook are a pair of balance forces. B. the pressure of physics textbook on desktop and the supporting force of desktop on physics textbook are a pair of interaction forces. C. the supporting force of physics textbook on stationery box and the pressure of stationery box on Physics Textbook are a pair of balance forces. D The support of the desk to the physics textbook and the pressure of the pencil case to the physics textbook are a pair of interaction forces

If the physics textbook is placed on the horizontal table and the pencil case is placed on the physics textbook, then () A. The gravity of physics textbook and the supporting force of desktop on physics textbook are a pair of balance forces. B. the pressure of physics textbook on desktop and the supporting force of desktop on physics textbook are a pair of interaction forces. C. the supporting force of physics textbook on stationery box and the pressure of stationery box on Physics Textbook are a pair of balance forces. D The support of the desk to the physics textbook and the pressure of the pencil case to the physics textbook are a pair of interaction forces

A. The gravity of the textbook and the supporting force of the textbook are not equal in size, opposite in direction, on the same straight line, on the same object, and do not meet the condition of equilibrium force. Therefore, a is wrong; B, the pressure of the physics textbook on the desktop is equal to the gravity of the stationery box plus the physics textbook, so the supporting force of the desktop on the physics textbook is equal to the pressure of the physics textbook on the desktop, which is in line with a pair of interaction forces Condition, so B is correct; C, the supporting force of the physics textbook on the pencil case is the pencil case, and the pressure of the pencil case on the physics textbook is the physics textbook, and these two forces do not meet the balance force condition of "the same object", so C is wrong; D, the supporting force in the option is equal to the gravity of the textbook, and the pressure is equal to the gravity of the pencil case, so the size is not equal, and it does not meet the mutual interaction So D is wrong. So B is chosen