You want tocreatea script that will determine if users were viewing a site before yours and if so, send an alert message to the users to tell them what Web site they came from to get to your site. What would the code look like to implement this?

a. If (navigator = true) {alert("You came from" 

+ document.referrer) }

b. If (document.referrer !=true) { alert("You came from" 

+ document.referrer) }

c. If (document.referrer =true) { alert("You came from" 

+ document.referrer) }

d. If (document.referrer !="") { alert("You came from" 

+ document.referrer) }