Final answer:
The statement is true; a comma should be used before the main clause when a subordinate clause begins the sentence, but no comma is needed if the subordinate clause ends the sentence unless it provides a contrast.
Step-by-step explanation:
The statement “When a subordinate clause begins the sentence, there should be a comma before the main clause. If the subordinate clause ends the sentence, there is no need for a comma.” is true. This is because a subordinate clause, also known as a dependent clause, cannot stand alone as a sentence and usually starts with a subordinating word such as 'although', 'because', 'if', etc.
When it precedes the main clause, a comma is needed to separate the two clauses. However, if the subordinate clause follows the main clause and does not imply a contrast (and is not nonessential), a comma is typically not used.
For example, in the sentence 'If you study hard, you will pass the exams,' ‘If you study hard’ is the subordinate clause and requires a comma before the main clause. Conversely, in the sentence 'You will pass the exams if you study hard,' no comma is necessary before 'if' since the subordinate clause comes after the main clause and does not express contrast.