Question

Convert compound sentence into simple sentence:
You must run fast, otherwise you can not catch the train
A) You must run fast in order to catch the train
B) You need run fast if you need to catch the train
C) To catch the train you must run fast
D) If you want catch the train you should run fast

Answer 1

Hint: Compound sentences are a type of simple sentence where more than one part of the sentence is present and every part is independent and makes complete sense itself. In every part of a compound substance, there is a separate subject and predicate.

Complete answer:
You must run fast, otherwise, you can not catch the train
In this sentence, there are two subjects used so this is a compound sentence. According to the question we have to change compound sentences into simple sentences. If we change the first clause of the sentence into a participial phrase then the compound sentence is converted into a simple sentence.
Option A: You must run fast in order to catch the train
In this sentence, there is one subject and the first clause is changed into a participial phrase. In this sentence, you cannot part change into in order. So it is the correct answer.
Option B: You need run fast if you need to catch the train
In this sentence, there are two subjects so it is not a simple subject
Option C: To catch the train you must run fast
In this sentence only one subject is present but in this sentence, there is no conversion of the first clause into a participial phrase.
Option D: If you want to catch the train you should run fast.
In this sentence, there are two subjects and one part is dependent on the other. So it is also not a simple sentence. It is a complex sentence.

Note:
A complex sentence has one dependent clause and the other is an independent sentence that makes complete sense. It has more than one subject.