Instead of submitting a copy of your teaching certificate with your application, you may submit verification that you are matriculated in a certification program (e.g., letter of acceptance, letter from advisor).
Expository writing is writing that seeks to explain, illuminate or 'expose' (which is where the word 'expository' comes from). This type of writing can include essays, newspaper and magazine articles, instruction manuals, textbooks, encyclopedia articles and other forms of writing, so long as they seek to explain.
Expository writing is crucial for students to get comfortable with since it will be needed in many potential careers that aren't primarily writing-oriented. Students must be able to organize their thoughts, follow a plan, and in higher grades, conduct research to support their theses.