Sally Fronson Sent an E-Mail to a Co-Worker on Her

Sally Fronson sent an e-mail to a co-worker on her employer's e-mail system that read,"I have had it with the long hours,the wages,and the attitude.Let's see if we can bring in a union." Which of the following is correct?​

A) ​Sally's e-mail is private and cannot be viewed by her employer.
B) ​Sally's e-mail is privileged and protected as union organizing and cannot be viewed by her employer.
C) Sally's e-mail is a permitted use and protected under the NRLA.
D) Sally can be terminated for private use of her employer's e-mail system.