3. a. Aluminium
It has the highest savings over 70% in energy & materials
B. Paper
Savings in materials is over 25%
Savings in energy is below 25%
It cannot be copper because the difference in savings for energy & materials will be really small compared to the differences in the savings for paper.
(For this question you're comparing the highest bar in materials - in the darker bar- then, comparing the highest differences in levels of savings compared to the energy bar)
Hope this helps!