The correct option is (c) .navbar-static-top
The best explanation: .navbar-nav is used on <ul> container that contains list items with links inside a navigation bar. .navbar-right aligns nav links, forms, buttons or text in navbar to the right. .navbar-static-top removes left, top and right borders (rounded corners) from navbar, default navbar has a grey border and 4px border-radius by default, .navbar-toggle styles button that should open navbar on small screens.