Final answer:
The sentence provided is indeed a complete sentence as it contains a subject, a verb, and expresses a complete thought.
Step-by-step explanation:
Yes, the sentence 'Mrs. Mason rummaged through the medicine cabinet for the thermometer.' is a complete sentence. A complete sentence must have at least a subject and a verb, and express a complete thought. In this sentence, 'Mrs. Mason' is the subject, and 'rummaged' is the verb.
The action described in the sentence forms a complete thought, telling us what Mrs. Mason did (the action of rummaging) and where she did it (through the medicine cabinet) for a specific purpose (to find the thermometer).
The sentence provides all the necessary elements for completeness with the inclusion of these details.