Solution

a-f : In the given sentence the subject should be in the plural form(friends) and the verb should be in the singular form(was). according to the “ Subject-Verb Agreement rule ”, “ One of/ Each of/ Most of + Plural Subject + Singular Verb ” is grammatically the correct structure.  b-d:   The adjective ‘recent’ is correct use in this context. Hence this sentence is correct. But it is incomplete. c-e: ‘Could’ is used to express possibility or past ability. Here in this sentence, the use of could is correct. hence option 5 is correct to - hence, option c is correct.