Two blocks are at rest on a horizontal frictionless surface with a compressed spring between them. The 10-kg block accelerates when the string holding the system in compression is cut and the 20-kg box accelerates in the opposite direction. What is the magnitude of the force from the expanding spring on the 20-kg box when the 10-kg box is undergoing an acceleration of 8.0 ?
选项：

A:40 N
B:160 N
C:(160/3) N
D:80 N
E:50 N
F:60 N G、100 N H、110 N I、120 N