Choosing an Effective Introduction

Read the following passage and answer the question that follows:

In the modern age, many people have developed a habit of multitasking. While some believe that multitasking increases productivity, others argue that it may lead to decreased performance in tasks that require focus. The effects of multitasking on attention and efficiency have been widely studied.

This passage would benefit from a clearer introduction that outlines the main argument. Which of the following sentences would best serve as a new introductory sentence?