There is a minor error in the explanation for the third one: the minimum allowed value for CHAR_BIT in C is 8 (it does not affect the result, principally because the value of ' ' could be anything in the range of char).
That's the one where I wanted most to quibble with the "explanation" of why there is no set answer: To me, the top of the line answer is that the value of the string constant ' ' as an integer is implementation-defined (or maybe it depends on the execution environment? See, I'll get the precise wording wong too); anyway, space is 32 in ASCII but 64 in EBCDIC. The most you could say is that it's not zero (and maybe that it's not -1? I'd have to check how EOF is defined)..
