Three statements are given followed by two conclusions numbered I and II. You have to take the statements to be true, even if they seem to be at variance with commonly known facts, and decide which of the conclusions logically follow(s) from the statements.
Statements:
I. Some Buses are Vans.
II. All Vans are Trucks.
III. Some Buses are Cars.
Conclusions:
(I) Some Trucks are Buses.
(II) Some Cars are Trucks.

​Statements:
I. Some Buses are Vans.
II. All Vans are Trucks.
III. Some Buses are Cars.​

According to the given statements, the possible Venn diagram is as follows:

Let's analyze the conclusions:

Conclusion I: Some Trucks are Buses. (True)

From the Venn diagram, it is evident that the circles representing bus and tuck intersect and overlap each other. So, from this, it can be concluded that some trucks are buses. Thus, this conclusion follows.

Conclusion II: Some Cars are Trucks. (False)

From the Venn diagram, it is evident that there is no direct relation cars and trucks. So, no definite relation can be concluded. Thus, this conclusion does not follow.

So, only conclusion (I) follows.

Thus, the correct answer is (b).