Social media can be a powerful communication tool for employees, helping them to collaborate, share ideas and solve problems. Research has shown that 82% of employees think social media can improve work relationships and 60% believe it can support decision-making processes. These beliefs contribute to a majority of workers connecting with colleagues on social media, even during work hours.

        Employers typically worry that social media is a productivity killer; more than half of U.S. employers reportedly block access to social media at work. In my research with 277 employees of a healthcare organization I found these concerns to be misguided. Social media doesn’t reduce productivity nearly as much as it kills employee retention.

        In the first part of the study I surveyed the employees about why and how they used platforms like Facebook, Twitter, or LinkedIn. Respondents were then asked about their work behaviors, including whether they felt motivated in their jobs and showed initiative at work. I found employees who engage in online social interactions with co-workers through social media blogs tend to be more motivated and come up with innovative ideas. But when employees interact with individuals outside the organization, they are less motivated and show less initiative.

        In the second part of the study I found 76% of employees using social media for work took an interest in other organizations they found on social media. When I examined how respondents expressed openness to new careers and employers, I found that they engaged in some key activities including researching new organizations and making new work connections.

       These findings present a dilemma for managers: employees using social media at work are more engaged and more productive, but they are also more likely to leave your company. Managers should implement solutions that neutralize the retention risk caused by social media.

        They can create social media groups in which employees will be more likely to collaborate and less likely to share withdrawal intentions or discussions about external job opportunities. Managers can also use social media to directly reduce turnover (跳槽) intentions, by recognizing employees’ accomplishments and giving visibility to employees’ success stories.

解析：C。根据题干中的the author find in his study和the effect of online social interactions可定位至原文第三段最后两句。该处提到，作者在其研究中发现，那些通过社交媒体博客与同事（co-workers）进行在线社交互动的员工往往更有动力，而且还能提出创新的想法。但是，如果员工是与公司以外人员（individuals outside the organization）互动，他们工作的积极性和主动性就会降低。由此可知线上社交互动的影响好坏与互动的对象有关，C项与此相符，故为正确答案。

错项排除：根据原文，决定线上社交互动影响的是互动的对象，而不是员工本身，故A项排除。原文第三段虽然提到三个社交平台，但并没有说是因为使用的平台不同而产生的影响不同，故B项错误。D项中的It is hard to measure在原文中无依据，故排除。