Question

http://imgur.com/BTF1D0b

Need help on a test.

Answer 1

These questions may help you think:
(a) How to find the area of a rectangle?

Answer 2

Sadly, I believe the question is ill-formed. I think it means l(t) IS the length, not the change in the length. Also, w(t) IS the width, not any change in width.

If it REALLY means "change", the answer is FAR more complicated than any of the options.

Answer 3

^agreed. Simple example to show why The left box has length and width 1 unit. Both are increased by 1 unit to get the box on the right.

According to this question, the change in the area should be the change in length times change in width... or 1*1, so an increase in area of 1 square unit.

Does it look like the area increased only 1 square unit