Answer:
The correct answer is option c. complete sentence.
Step-by-step explanation:
A complete sentence must have a subject and a predicate.
The subject is who performs the action or whose something is said.
In this case the subject is Slalom skiers.
The predicate is the part that describes the action, and there should always be a verb that matches in person and number with the subject.
In this case "race against the clock."
Therefore, the sentence "Slalom skiers race against the clock." is a complete sentence.
The correct answer is option C.