The correct answer is: B. Paper clip Icon
A paper clip icon is the standard indicator for an attachment in an email client. It is a small, graphical representation of a paper clip that is used to indicate that an email message contains an attachment. The paper clip icon is typically located next to the subject line of the email message.
The other options are incorrect because they are not typically used as indicators for attachments in email clients. A clip icon is a generic icon that can be used to represent a variety of things, including attachments. A stationary icon is an icon that is used to represent stationery, such as paper and envelopes. A gif icon is an icon that is used to represent a moving image, such as a GIF file.