An email with a clear subject and polite language shows which communication?

Correct answer: Written communication

The direct answer is C: written communication. An email communicates information through written words and is sent electronically, so it is a form of written communication. A clear subject tells the reader what the message concerns; polite language shows professionalism and respect; organized sentences make the message easier to understand. Step by step: write a specific subject; greet the reader appropriately; state the purpose clearly; provide necessary details; use respectful language; check spelling and send a suitable closing. Option A, physical signal, refers to bodily actions such as gestures or posture, not an email. Option B, verbal argument, means a spoken disagreement and does not describe a polite written message. Option C is correct because the email uses written text to convey the message. Option D, informal joke, describes a type of casual content, not the communication mode shown here. A professional email may be friendly, but clarity and respect remain important. Memory cue: email + written words = written communication.