Multi-choice problem: Continue writing the next sentence in this paragraph:

How to make rainbow chocolate chip cookies 
Prepare the oven and tray. 
Preheat the oven to 350 degrees fahrenheit or 176 degrees celsius. Cover a baking tray with parchment paper or spray non-stick greasing spray on it.

Pick your answer from:
(a). Spray the tray with nonstick cooking spray. You don't need to cover the tray at all, just spray the baking tray with non-stick cooking spray to help make sure it's dry.;
(b). Prepare the cookie sheet by laying out baking paper or using a baking tray. Make sure that the tray is shallow enough for the cookie sheet to sit perfectly.;
(c). Combine the flour, baking soda, and cornstarch with a whisk. Stir until the dry ingredients are mixed properly.;
(d). Ensure the sheet of parchment paper is easily accessible by opening it to show your cookie mix pile. Mix the chocolate chips in a bowl.;
(c).