To solve this problem, we need to determine the accelerations of blocks A and B immediately after the string is cut.$\\$Initially, the system is in equilibrium, so the spring force balances the gravitational force on the entire system.$\\$When the string is cut, block B is no longer supported by block A, and both blocks will experience free fall.$\\$Let's analyze each block separately:$\\$1. Block A (mass $3m$):$\\$• After the string is cut, block A is only acted upon by gravity.$\\$• The acceleration of block A is equal to the acceleration due to gravity, $g$.$\\$2. Block B (mass $m$):$\\$• Similarly, block B is also only acted upon by gravity after the string is cut.$\\$• The acceleration of block B is also $g$.$\\$Therefore, the magnitudes of acceleration of A and B immediately after the string is cut are both $g$.$\\$This corresponds to Option 2: $g, g$.