Option 1: (C), (B), (D), (A) -> Forms: "Being given to understand that there was a vacancy for an assistant in the firm, an application was submitted by me" - grammatically correct with proper subordinate clause structure.
Option 2: (A), (D), (C), (B) -> Creates a fragmented sentence starting with "was submitted by me" - lacks proper sentence flow.
Option 3: (B), (C), (D), (A) -> Results in awkward construction where "being given to understand that" breaks the natural flow mid-sentence.
Option 4: (D), (B), (C), (A) -> Produces a completely jumbled sentence with no logical coherence.
Hence, Option 1: (C), (B), (D), (A) -> This creates a grammatically sound complex sentence with a participial phrase ("Being given to understand that...") introducing the subordinate clause, followed by the main clause. The sentence logically explains that upon learning about a vacancy, the speaker submitted an application -> correct