Lana Applies for a Firefighter's Job with Metro City,which Responds

Lana applies for a firefighter's job with Metro City,which responds with a letter setting an appointment for a medical exam. The letter also states that it is "an employment offer conditioned on the applicant passing the exam." This letter is

A) a bilateral contract that Lana accepted by applying for the job.
B) a quasi contract on which Lana can rely for employment.
C) a unilateral contract that Lana can accept by passing the exam.
D) no contract.