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 a type of writing where the purpose is to explain, inform, or even describe. It is considered to be one of the four most common rhetorical modes. The purpose of expository writing is to explain and analyze information by presenting an idea, relevant evidence, and appropriate discussion.