The characteristics of a good email message include:
A. It is short and to the point.
B. It is polite and respectful.
D. It states the unit and lesson number you are referring to.
E. It states the subject of the course you are writing about.
C. It is written in all caps. (This is generally not considered a good characteristic, as writing in all caps can be interpreted as shouting and is often viewed as unprofessional.)