HTML/CSS Assessment questions about the 600px

Hi,
I am working on the HTML assessment and I am stuck on this portion:

    • … is 600px wide when the screen is greater than or equal to 600px wide
    • … uses grid layout to layout labels and form elements when the screen is greater than or equal to 600px wide
    • … is the width of the screen when the screen is less than 600px wide
    • … lays out the labels and form elements as full width when the screen is less than 600px wide

I’m not sure if I am on the right track or not. Whenever I change the resolution of the page, I can’t see to get the fieldset’s width to change.
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