Statements: All jungles are buses. All books are buses. All fruits are books. Conclusions:  Some fruits are jungles. Some buses are books. Some buses are jungles. All fruits are buses.

III is the converse of the first premise and II is the converse of the second premise.

So, both of them hold.

All fruits are books. All books are buses.

Since both the premises are universal and affirmative, the conclusion must be universal affirmative and should not contain the middle term. So, it follows that 'All fruits are buses'. Thus, IV follows.

All jungles are buses. All books are buses.

Since the middle term 'buses' is not distributed ever once in the premises, no definite conclusion follows.

All fruits are buses. All books are buses.

As discussed above, no definite conclusion can be drawn.

All jungles are buses. All fruits are buses.

Again, no definite conclusion follows.