Suppose that we are given a relation schema r with four attributes, abcd, and the set of fds f = { ab  c, bc  d, d  a }. assuming those are the only dependencies that hold for r, answer the following questions (justify briefly your answers): (a) is ac a key of r? (b) is ab a key of r? (c) what is a prime attribute? is attribute a a prime attribute? (d) is r in 3rd normal form (3nf)? (e) is r in boyce-codd normal form (bcnf)

What part of the interface displays the external references contained in a selected cell? the status bar the review tab the scroll bar the formula bar

What is the difference between the internet and the world wide web?

1. web and mobile applications allow users to be actively engaged in an online activity. a true b false 2. some examples of business applications purposes are to collaborate, share files, meet virtually in real-time, and accept payments. a true b false 3. an education application would most likely do which of the following? a allow users to watch popular movies and tv shows b connect users with social and business contacts c confirm users' travel plans d teach users a new language 4. a uniform resource locator (url) is how the internet knows where to take users when an address is typed into a browser. a true b false 5. deon is required to provide the citation information for his sources. what type of information should he collect from his sources? a author name, title, date of publication, date of access, url b connections to background information c interesting facts and statistics d notes on important information