A. Yes and no. Windows Phone 7 doesn't support removable storage in the sense that you can't insert an SD card then remove. It does support extendable storage in that you can insert an SD card into a phone that supports it, but you can't remove it, because that SD storage becomes part of the phone's internal storage—if it's removed, it will cause an error. Windows Phone 7 also formats the SD card in a proprietary format, so once it's been used by a Windows Phone 7, device the SD card can't be read or used by another platform.
A word of caution: Some of my friends put in SD cards and say their devices now run slower. This could be because the SD storage is slower than the internal storage, and because data is spread over the SD card and internal storage, it slows down the overall experience.