These are True and False

Is possible - Please give an explanation, Thank you.

Question 1 Comparing to a typical file system, a DBMS provides a higher level of abstraction for problem solving. Question 2 A table in Microsoft's Access must have at least one column. Question 3 A relation may not have any foreign key. Question 4 One advantage of DBMS over a file system is its higher degree of concurrent accesses. Question 5 A and AB cannot be superkeys of R at the same time. Question 6 The Excel spreadsheet's data model is set-theoretic. Question 7 A prime attribute may have a null value