Question

What are the characteristics of effective subject lines? brief eliminate the need to read the complete message include humor tell what the message is about

Answer 1

They are brief.

They tell what the message is about.

Answer 2

The right answer is "tell what the message is about".

The explanation for this is the subject line is the part of the email that subscribers see when it lands in their inbox. They use it to judge whether an email is worth opening.