The reply email field opens with the highlighted quote already positioned in the body of the email.
Just add your response and send it on its way.
MacOS andiOSMail work this way.

No two email programs use the exact same reply procedure.
In almost all cases, the quoted information is indented to make it easy to recognize.
In some email programs, the quoted material appears in a different color.
Begin your email with a salutation and an introductory comment.
Next comes the quoted material.
Your response to the quote then appears beneath it.