In-situ questions are only very rarely attested, and only under specific discourse conditions. Fronting of wh-phrases is virtually obligatory. A fronted wh-phrase is optionally marked for focus.
Source: Kouwenberg 1994: 40
Source: Kouwenberg 1994: 41
Source: Kouwenberg 1994: 42
Source: Kouwenberg 1994: 44
Source: Kouwenberg 1994: 44