A new roof-rack system features cross bars that stow in the roof rails when not in use, helping to reduce drag and give fuel economy an extra boost.是什么意思_A new roof-rack system features cross bars that stow in the roof rails when not in use, helping to reduce drag and give fuel economy an extra boost.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句