I clean my room so I can play.
The answer is number 4) These numbers show that teenagers care about others.
Sentences 1-3 show evidence to support the main argument, which is that teenagers help others. Sentence 1 gives an individual example, and on sentences 2 and 3, it presents statistical data.
An implied argument is an argument which leaves us to draw the supposedly obvious conclusion for ourselves. Where an assumption on which the argument depends is not stated it is not readily available for scrutiny and therefore the fact that it is questionable or false can easily escape our attention. Similarly where a conclusion remains unstated the questionable connection between it and the reasons given for it remains out of view and may thus escape our critical appraisal. The problem with implied arguments therefore is that they involve a sort of mental sleight of hand that can fool us.
The only element among these that are to be used in a formal letter are complex sentences.
As a matter of fact, idioms, contractions, and cliches should be avoided because they are very informal.
