Different options it could be
Structure of letter
Persuasive techniques
Opening ideas
Persuasive techniques CEMSERPAC
Counter argument
Exaggeration
Metaphor
Simile
Emotive language
Rhetorical question
Prolepsis
Anecdote
Comparison
Persuasive techniques ICTERSQC
Imperative
Collective pronouns
Tricolon
Emotive language
Rhetorical question
Statistics
Quotation
Climax