which of the following is a feature of an effective business email

the subject line is in all capital letters
the message has a number of abbreviations in order to save the writer time
the subject line clealrly states what email is about
the message has a joke in the last paragraph

The feature of an effective business email among the options provided is:

- The subject line clearly states what the email is about

The feature of an effective business email is that the subject line clearly states what the email is about.