Why Inductors in parallel combine like resistors in parallel: 1/Lt = 1/L1 + 1/L2 + 1/L3. With N identical inductors the total is simply L/N, so 10 mH divided by 3 gives about 3.3 mH. The result is always smaller than the smallest inductor in the group.
Watch out The 30 millihenry answer is what you would get by adding them, which applies to inductors in series, not parallel. The henry-valued choices are off by a factor of 1000 from the millihenry units given.
Inductors act like resistors: series adds, parallel divides. Equal parts in parallel = value/N, and answer stays in mH.