Since ab³c⁴is negative and c⁴ is positive, then in ab³ one variable is positive and the other negative. Hence ab<0, or negative, so Ⅰ is false and Ⅱ is true. Now let’s look at Ⅲ. You know ab is negative — but you don’t know a thing about C. It could be positive or negative. So cross out E..