Correct Answer - Option 2 : {(ab)
n cb
m1 cb
m2 … cb
mn |n, m
1, m
2 … , m
n ≥ 1}
String Derivation:
S → abScT
→ ababScTcT (∵ S → abScT)
→ abababcTcTcT (∵ S → abcT)
→ abababcbTcTcT (∵ T → bT)
→ abababcbbTcTcT (∵ T → bT)
→ abababcbbbTcTcT (∵ T → bT)
→ abababcbbbbcTcT (∵ T → b)
→ abababcbbbbcbcT (∵ T → b)
→ abababcbbbbcbcbT (∵ T → bT)
→ abababcbbbbcbcbb (∵ T → b)
abababcbbbbcbcbb = (ab)3cb4cbcb2
From this string, it is clear that all the option 1),3) and 4) are not generated by given grammar.
Only option 2 matches.