Concept:A complex sentence combines an independent clause with one or more dependent clauses using subordinating conjunctions or relative pronouns. To convert a simple sentence starting with "because of" (a phrase) into a complex sentence, replace the phrase with a subordinating conjunction like "since" or "because" followed by a full clause.
Explanation:1. The given simple sentence is: "Because of the rain, he could not attend the exam on time." The phrase "Because of the rain" acts as an adverbial prepositional phrase.
2. To make it complex, we need a dependent clause that expresses the reason. The conjunction "since" can introduce such a clause.
3. Convert "the rain" into a clause: "it was raining".
4. Combine: "Since it was raining, he could not attend the exam on time." This has a dependent clause ("Since it was raining") and an independent clause ("he could not attend the exam on time").
5. Check options: Option A matches. Options B changes meaning, C and D are still simple sentences (they use "because of" or no clause change).
Answer:Option A: Since it was raining, he could not attend the exam on time.