The correct option is B 6 H
Let the inductances of the inductors be L1 and L2.
If connected in series,
Leq=L1+L2
10=L1+L2 ...(i)
When connected in parallel,
Leq=L1L2L1+L2
⇒2.4=L1L2L1+L2 ...(ii)
From equations (i) and (ii),
L1L2=24 ...(iii)
Also,
L1−L2=√(L1+L2)2−4L1L2
⇒L1−L2=√102−4×24 [From (i) and (iii)]
⇒L1−L2=2 ...(iv)
On solving equations (i) and (iv), we get, L1=6 H and L2=4 H
Hence, option (B) is the correct answer.