Explanation:

To answer this question, we need to understand the different types of conjunctions and how they are used in transforming simple sentences into compound sentences.

Conjunctions:
Conjunctions are words that connect different parts of a sentence. They are used to join words, phrases, or clauses together. There are different types of conjunctions, including coordinating conjunctions, subordinating conjunctions, correlative conjunctions, alternative conjunctions, illative conjunctions, cumulative conjunctions, and complex conjunctions.

Transformation of Simple Sentences into Compound Sentences:
When transforming a simple sentence into a compound sentence, we use conjunctions to join two independent clauses together. This helps to combine two related ideas into a single sentence. The conjunction used depends on the relationship between the two clauses.

Types of Conjunctions Used in Transformation:
a) Alternative Conjunctions:
- Examples: either...or, neither...nor
- Used to present a choice or alternative between two options.
- Example: I can either go to the park or stay at home.

b) Illative Conjunctions:
- Examples: therefore, thus, so, hence, consequently
- Used to show cause and effect or to draw a conclusion.
- Example: He studied hard; therefore, he passed the exam.

c) Cumulative Conjunctions:
- Examples: and, also, moreover, in addition, furthermore
- Used to add information or ideas to the previous clause.
- Example: She loves to read, and she enjoys writing as well.

d) Complex Conjunctions:
- Examples: although, because, if, since, unless
- Used to show a relationship between two clauses, where one clause is dependent on the other.
- Example: Although it was raining, they still went for a walk.

The Correct Answer:
The correct answer is option 'D' - Complex conjunctions. Complex conjunctions are not used in the transformation of simple sentences into compound sentences. Instead, they are used in the transformation of simple sentences into complex sentences by introducing a dependent clause.