Which of the following is the correct syntax to add an iframe?

• A. <iframe src = " demo_iframe.htm " style = " border:none " > < / iframe >
• B. <iframe src = " demo_iframe.htm " style = " border:5px dotted red " > < / iframe >
• C. <iframe src = " demo_iframe.htm " width = " 200 " height = " 200 " > < / iframe >
• D. <iframe src = " URL " >< / iframe>