以下表达都可以:* n; b' T" U; X& |: b
1 v$ Z1 ]1 Y3 w4 L' |3 D
1. soldiers must first pass a six-month advanced training 6 m& z8 c# `3 q M2. soldiers must first pass a six months' advanced training8 l. R/ T9 I( R; H% |
3. soldiers must first pass six months of advanced training0 N/ w6 v% M! d6 X, L" N