某位廣告主準備好建立行動廣告活動，並希望廣告能在任何新式瀏覽器上放送。 請問他應該選用哪種廣告空間？

The advertiser wants to run a mobile campaign that works across modern browsers. Smartphone and tablet inventory is the most appropriate choice because these devices are designed for modern web browsing and encompass the primary mobile user base. While "smartphone and desktop website inventory" includes smartphones, it unnecessarily adds desktop, which isn't the focus. "Mobile app in-app and in-stream video inventory" and "mobile app in-app and out-stream video inventory" are too restrictive, focusing only on apps and specific video formats, rather than general mobile browsing across modern browsers.