Two forces `F_(1)` and `F_(2)` are acting on the system according to figure. Match Column-I and Column-II
`f r_(1)rarr` Friction force between blocks
`f r_(2)rarr` Friction force between lower block and ground
T `rarr` Tension in string

`{:("Column I",,,"Column II"),((A) "If "F_(1)=8N.F_(2)=18N,,,(P)f r_(1)=8N),((B)"If "F_(1)=12N.F_(2)=12N,,,(Q)f r_(1)=4N),((C )"If "F_(1)=4N.F_(2)=20N,,,(R)f r_(2)=10N),((D)"If "F_(1)=8N.F_(2)=0N,,,(S)"Tension in the string is zero"),(,,,(T)"Upper block moves"):}`

Answer

(A - Q, S, T), (B - S S, T), (C - Q, S, T), (D - P, S, T)

Explanation

(A) Both spheres stick to each other. (B) A stops and B moves rightwards with speed `v_(0)`
(C ) Both move right-ward (D) M `gtgt` m and collision is elastic.