2j-r

3j-r

j-2r

j-3r

1

2

3

6

unstable

stable and statically determinate

stable and statically indeterminate

none of the above

internal forces only

external forces only

internal as well as external forces

none of the above

for statically determinate structures only

when the system behaves elastically

only when principle of superposition is valid

none of the above