Which of the following attacks specifically impact data availability?

Describe the relations that would be produced by the following tuple relational calculus expressions:

(a) {H.hotelName | Hotel(H) ? H.city = ‘London’} (b) {H.hotelName | Hotel(H) ? (?R) (Room(R) ? H.hotelNo ? R.hotelNo?? R.price ?50)} (c) {H.hotelName | Hotel(H) ? (?B) (?G) (Booking(B) ? Guest(G) ? H.hotelNo ? B.hotelNo?? B.guestNo = G.guestNo ?? G.guestName = ‘John Smith’)} (d) {H.hotelName, G.guestName, B1.dateFrom, B2.dateFrom | Hotel(H) ? Guest(G) ? Booking(B1) ? Booking(B2) ? H.hotelNo ? B1.hotelNo?? G.guestNo = B1.guestNo ?? B2.hotelNo = B1.hotelNo ? B2.guestNo = B1.guestNo ?? B2.dateFrom ? B1.dateFrom}

To enhance security, an e-commerce site should implement _____ technology to encrypt sensitive customer information.?

A. ?secure socket layer B. ?plug-and-play  C. ?bit mapping layer D. ?integrated route security