Solution:(b) Unpublished authors were being expected by the magazine house for their forthcoming exclusive issue on new trends.(a) Unpublished authors will be expected by the magazine house for their forthcoming exclusive issue on new trends. (Incorrect Tense)
(c) Unpublished authors was expected by the magazine house for their forthcoming exclusive issue on new trends. (Incorrect Helping Verb)
(d) Unpublished authors were expected by the magazine house for their forthcoming exclusive issue on new trends. (Incorrect Helping Verb)