Mr$.$ Smith, a public elementary school custodian, is a Seventh Day Adventist. His religious beliefs prevent him from working from sundown Friday to sundown Saturday. The work schedule, which requires him to work a Friday shift from $3$ p$.$m$.$ to $11$ p$.$m$.,$ is set out in the collective agreement between his employer and his union. Accommodating Mr$.$ Smith's religious beliefs would require allowing him to work hours different from those specified. The employer and the union can't agree on a means of accommodating Mr$.$ Smith. As a result, he is dismissed from his job.

What legally protected ground may be violated in this situation?

race

religion

ethnic origin

sex