3、_____________________三、简答题(每题4分,共16分)24.(4分)(1)(2)(3)(4)_______25.(4分)(1)________________(2)(3)(4)________26.(4分)(1)_______________(2)(3)___________________________________________________________27.(4分)(1)(2)___________(3)_________ 四、实验题(共30分)28.(7分)(1)① ; ②