The difference between the two is, well for one
Spectrum: The entire range that the "<em>waves" </em>could be such, as visible light, x-ray's and so on.
Waves: These are different because they aren't telling you or showing the entire spectrum just which they length that they are.
<em>It may confuse you but it makes sense to me (Sorry)</em>
I think I can answer your question since I've worked on this before.
Your answer should be obtain energy.
If your answer choices were;
obtain energy
escape predators
produce offspring
excrete waste
Explanation:
First we will convert the given mass from lb to kg as follows.
157 lb = 
= 71.215 kg
Now, mass of caffeine required for a person of that mass at the LD50 is as follows.

= 12818.7 mg
Convert the % of (w/w) into % (w/v) as follows.
0.65% (w/w) = 
= 
= 
Therefore, calculate the volume which contains the amount of caffeine as follows.
12818.7 mg = 12.8187 g = 
= 1972 ml
Thus, we can conclude that 1972 ml of the drink would be required to reach an LD50 of 180 mg/kg body mass if the person weighed 157 lb.
The answer is C. An occluded front.