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.
The procedures the article lists on how to teach expository text are great. Students need to learn the difference of the texts that they will be reading. As the article states, knowing what type of text is being read leads to having a plan for reading and knowing what to expect from the reading.