Statements : All pencils are birds. All birds are skies. All skies are hills.

Conclusions :
I. All pencils are hills.
II. All hills are birds
III. All skies are pencils.
IV. All birds are hills.

Explanation:-

All pencils are birds. All birds are skies.

Since both the premises are universal and affirmative, the conclusion must be universal affirmative (A-type) and should not contain the middle term. So, it follows that 'All pencils are skies'.

All birds are skies. All skies are hills.

As discussed above, it follows that 'All birds are hills'. Thus, IV follows.

All pencils are skies. All skies are hills.

Clearly, it follows that 'All pencils are hills'. Thus, I follows. Hence, I and IV follow.