16. To be called object-oriented, a programming language must allow

A. functions that return only a single value
B. #include files
C. inheritance
D. All of the above

17. A function that returns no values to the program that calls it is _____

A. not allowed in C++
B. type void
C. type empty
D. type barren

18. The keyword used to define a structure is _____

A. stru
B. stt
C. struct
D. structure

19. If container classes are carefully constructed, then these tools are available to work with structures that are not ______

A. valid without container classes
B. programmer-defined
C. type-specific
D. public

20. Header files often have the file extension _____

A. .H
B. .HE
C. .HEA
D. .HEAD