(A) Determine all possible non zero real P such that {P}, [P] and P are in arithmetic sequence.

(B) Determine all possible non zero real Q such that {Q}, [Q] and Q are in geometric sequence.

(C) Determine all possible non zero real R such that [R], {R} and R are in geometric sequence.

(D) Determine all possible non zero real S such that {S}, [S] and S are in harmonic sequence.

Note: [x] is defined as the greatest integer ≤ x and {x} = x - [x]