C++ help

20. Which of the following classes is the base class of the other three? (a) ios (b) istream (c) ostream (d) iostream Which of the following is not a member of the ostream class? (a) cout (b) cerr (c) cin (d) clog Which of the following is not a member function of the C++ ostream class? (a) insertion ( (c) put (d) write Which file open mode would be used to write data only to the end of an existing file? (a) ios::app (b) ios::in (c) ios::out (d) ios::trunc