What is the appropriate parameter for the alert() method in line 5 to reference the text in the firstName text box?

Consider the following code:

What is the appropriate parameter for the alert() method in line 5 to reference the text in the firstName text box?(Exhibit)

A.
document.myForm.value(firstName)

B.
document.myForm.firstName.value

C.
window.myForm.firstName.value

D.
window.myForm.text(firstName)