Final answer:
The sentence should be completed with 'Each employee is expected to sign a waiver before participating in the race.', as the subject 'Each employee' is singular and requires a singular verb.
Step-by-step explanation:
The correct word to complete the sentence "Each employee is expected to sign a waiver before participating in the race." is 'is'. Here, 'Each employee' is the subject of the sentence, which is singular, hence the singular verb 'is' should be used. It is important to match the verb to the subject in number and person for proper sentence construction.