Rule 26 of the Federal Rules of Civil Procedure covers discovery. Smarty Pants has been retained as an expert witness in a civil litigation matter. Smarty Pants may be called to testify at trial. Opposing counsel wants to depose Smarty Pants prior to trial. Which of the following is TRUE

?Smarty Pants can be deposed only after he has provided a written report.

Smarty Pants cannot be deposed.

Smarty Pants can be deposed at any time.

Smarty Pants can be deposed if he agrees to being deposed.