Conclusions:
I. All Drivers can be Conductors.
II. Some Tractors are Cars.
III. Few Cars are not Tram.  Statements: 

From Statement I. Some Drivers are Trams (I) + Some Trams are Conductors (I) → Probable conclusion → All Drivers can be Conductors (A). Hence conclusion I follows. Only Conductors are Cars → All Cars are Conductors and Cars cannot have positive relation with anyone. Hence conclusion II does not follow but conclusion III follows.   From Statement II. All Drivers are Cars (A) + [All Conductors are Cars (A) → Conversion → Some Cars are Conductors (I) → Probable conclusion → All Drivers can be Conductors (A). Hence conclusion I follows. Some Tractors are Conductors (I) + All Conductors are Cars (A) → Some Tractors are Cars (I). Hence conclusion II follows. No driver is a Tram (E) → Conversion → No Tram is a Driver (E) + All Drivers are Cars (A) → Some Cars are not Tram (O*). Hence conclusion III follows. From Statement III. Some Drivers are Conductors (I) → Probable conclusion → All Drivers can be Conductors (A). Hence conclusion I follows. All Cars are Tractors (A) → Conversion → Some Tractors are Cars (I) Hence conclusion II follows. All Cars are Tractors (A) + Only a few Tractors are Trams (I) → No conclusion. Hence conclusion III does not follow. From Statement IV. All Conductors are Cars (A) + All Cars are Tractors (A) →   All Conductors are Tractors (A) + All Tractors are Trams (A) → All Conductors are Trams (A) + No Tram is a Driver (E) → No Conductor is a Driver (E). Hence conclusion I does not follow. All Cars are Tractors (A) → Conversion → Some Tractors are Cars (I) Hence conclusion II follows. All Cars are Tractors (A) + All Tractors are Trams (A) → All Cars are Trams (A). Hence conclusion III does not follow.