< means 'less than'. 3.5 is less than 4.5, so A is correct. Since -4.5 is NEGATIVE it is less than 0. As for C, since both numbers are negative, it would be the seemingly 'smaller' number that is actually bigger. It may help to think of the numbers on a number line. In the negatives, the numbers start to go in reverse, so the further from 0 a negative number is, the smaller it is. -4.5 IS LESS than -3.5. All answers are correct.
I assume by the length you mean height so,

≈ <span>4.54
.
if you're supposed to round it, it'd be either 4.50, or 5
</span>
I hope this helps