The strings of Option (a) and (b) can be generated by the given grammar as follows:
(a) E --> T + E => T+T+E => T+T+T => T+T+F=>T+F+F => F+F+F =>F+F+id =>F+id+id => id+id+id
(b) E --> E * T => E*T*T => T*T*T =>F*T*T=>F*F*T => F*F*F => id *F*F=> id*id*F=> id*id*id
but the string (id *id *id) cant be generated as ( ) must be included into the reduction of (T*F) to T.
So the answer should be option (c).