When Bob went to work as a software engineer for a tech start$-$up company, his employment contract stated he was "employed at will and could be terminated at any time." After $15$ months with the company, he was fired without explanation. Which of the following statements is true?

Question $24$ options:

Bob could only be fired for just cause.

Because Bob had an employment contract, he was not an employee at will.

Bob could be fired for any reason except an unlawful reason.

Bob could be fired for any reason, but the company must provide an explanation for his termination.