Question

Whether you write a one page résumé, a two page résumé, or a combination of both, what is the key to writing an effective résumé

Answer 1

I'm confused - is this a multiple choice question or a fill in the blank.

The key to  creating an effective resume is selling your skills. You want your employer to think you are the best option out there, and the one they should select for the job.

Answer 2

Clear and concise representation of your most relevant information is the key to write an effective resume.

The purpose of writing the resume is to reflect your unique education, experience and relevant skills. While doing the same, the ideal approach is to put the information in a simple and straightforward manner so that it is easy for the employer to understand and evaluate your profile. A complex resume reduces the chances of selection, as the employer might lose interest in the early stages of selection.