-Supporting Evidence This is the right option.
The claim is: High school students should study a language . To strengthen this idea evidence is needed. For example, the evidence can include the relationship between studying a language - which may refer to a foreign one- and the positive results this may have in different areas. These can be: improvement in cognitive skills, in general; improvements in mother tongue; and getting more tools to face the labour market.
These options are not right:
-An Informal Tone ( The statement has a presciptive tone not a friendly tone. It sounds like a formal statement not like a conversational exchange).
-A Clear Opinion ( The statement is a generalization , so it needs objective evidende.)
-Lively Language ( The statement does not sound as if it were from a commercial).