The correct answer is: Only conclusion II follows.
The first statement, “Some books are pens,” means that there exists at least one book that is also a pen. The second statement, “No pen is pencil,” means that no pen is a pencil.
From these two statements, we can conclude that no book is a pencil. This is because if a book were a pencil, then it would be a pen, which contradicts the second statement. However, we cannot conclude that some books are pencils. This is because the first statement only tells us that there exists at least one book that is also a pen. It does not tell us that all books are pens.
Therefore, only conclusion II follows.