Which sentence uses punctuation correctly
a.
since i was a young child my parents have raised me to be polite to everyone.

b.
even if they are friendly to me i'm not always sure what to say to other people.

c.
i try to listen carefully when people are speaking directly to me

None... unless it's B... I'd say C but it has no period... so B xD

The two word phrase could be:  "For Every"

When we are writing a ratio or fraction, we are comparing two different quantities. 

Imagine that a track athlete has to run 3 miles for every day of practice. We could write the ratio 3:1.

Imagine that your parents are going to pay you $15 for every A on your report card. We could write the ratio 15:1

The key words are "For Every".