Because the size of atoms increase as you move down the periodic table.
I think that a writer may use all of the following techniques to lead the reader to a flashback EXCEPT: a. a memory
Answer:

Explanation:
We are given the percent composition: 22.5% phosphorus and 77.5% chlorine.
We can assume there are 100 grams of this compound. We choose 100 because we can simply use the percentages as the masses.
Next, convert these masses to moles, using the molar masses found on the Periodic Table.
- P: 30.974 g/mol
- Cl: 35.45 g/mol
Use the molar masses as ratios and multiply by the number of grams. 

Divide both of the moles by the smallest number of moles to find the mole ratio.


The mole ratio is about 1 P: 3 Cl, so the empirical formula is written as:<u> PCl₃</u>
The conversion for cm³ to ml is:
1 cubic centimetre = 1 millimetre
Therefore,
2 cubic centimetres = 2.0 millimetres
And so, your answer is E (but the cm should be cm³).