Totally makes sense picking A and D, since SAP Business Application Studio is the go-to for pro devs and SAP Build covers low-code/no-code scenarios. HANA Cloud is just for database, so not actually a dev environment. The question clearly asks about building the app, not just hosting data or making a portal. Think that's right but open to debate if someone sees another use case here.
D imo. A and D are both actual dev tools on SAP BTP for building custom apps, which is exactly what the question asks about. C trips folks up since HANA Cloud is for data persistence but not meant for developing the app itself. B is more about building sites or portals, not standalone apps. Seen variations of this in practice sets, so I think A/D is solid here. Disagree?
Its A and D, both are part of SAP BTP for developing and integrating custom apps. Quick check, if the requirement was to make a portal instead of an app, B could fit but not here.