[单选题]
A spring-mass system executevw2i as96 1p4q)8+ c:uenjsb tqpe3zxka9u9l s simple harmonic motiwn)n6rjxalah)+ u5; qon with an amplitude of 20cm and maximum elastic potential energy oalrxj +nwq6a)nhu; )5f 100J. What is the displacement of the mass when the elastic potential energy of the system is 25J?