Two months will have the same calender if the period between them is divisible by 7.
Now,
(a). June + July + Aug. + Sep. = 30 + 31 + 31 + 30 = 122 (not divisible by 7)
(b). Apr. + May + June + July + Aug. + Sep. + Oct. = 30 + 31 + 30 + 31 + 31 +30 + 31 = 213 (not divisible by 7)
(c). Apr. + May + June = 30 + 31 + 30 = 91 (divisible by 7)
(d). October + November = 31 + 30 = 61 (not divisible by 7)