The correct answer is: Both I and II follow.
The first statement is “All fish are tortoise.” This means that every single fish is also a tortoise. The second statement is “No tortoise is a crocodile.” This means that no tortoise is a crocodile.
From the first statement, we know that all fish are tortoise. From the second statement, we know that no tortoise is a crocodile. Therefore, we can conclude that no fish is a crocodile. This is because if a fish were a crocodile, it would be a tortoise, but we know that no tortoise is a crocodile.
We can also conclude that no crocodile is a fish. This is because if a crocodile were a fish, it would be a tortoise, but we know that all fish are tortoises.
Therefore, both conclusions I and II follow.