is this true:Introductory participial phrases and adverb clauses are set off from main clauses by commas.

Yes, it's true.

See #3 here:
http://grammar.ccc.commnet.edu/grammar/commas.htm

Well, my friend, it seems like you've stumbled upon a grammatical dilemma. While it's true that introductory participial phrases and adverb clauses can often be accompanied by commas, their usage isn't always so straightforward. You see, the comma usage depends on various factors, such as the specific context and intended meaning of the sentence. So, to answer your question with a dash of humor and a sprinkle of truth: It's kind of true, but also kind of not true. Grammar can be a bit of a prankster, don't you think?

Yes, the statement is true. Both introductory participial phrases and adverb clauses are set off from main clauses by commas. Commas are used to separate these introductory elements from the main clause to provide clarity and avoid confusion in sentence structure.

Yes, it is true that introductory participial phrases and adverb clauses are set off from main clauses by commas.

Now, I will explain how to identify and set off these phrases and clauses.

1. Introductory Participial Phrases:
A participial phrase is a phrase that begins with a present or past participle (-ing or -ed verb form) and acts as an adjective, providing more information about a noun or pronoun. When a participial phrase appears at the beginning of a sentence, it is usually set off by a comma.

Example:

Walking slowly along the path, Sarah enjoyed the peacefulness of the forest.

In this example, "Walking slowly along the path" is the introductory participial phrase, providing information about Sarah. The phrase is set off by a comma.

2. Introductory Adverb Clauses:
An adverb clause is a group of words that functions as an adverb, modifying a verb, adjective, or adverb and providing information about time, place, condition, manner, or reason. When an adverb clause begins a sentence, it is typically set off by a comma.

Example:

Before she left for work, Jane made breakfast for her family.

Here, "Before she left for work" is the introductory adverb clause, indicating a time relationship. The clause is separated from the main clause with a comma.

It's important to note that not all participial phrases or adverb clauses require a comma. The use of a comma depends on whether the phrase or clause is essential for the meaning of the sentence. If the phrase or clause is essential, meaning its removal would change the meaning of the sentence, then no comma is needed. But if the phrase or clause is non-essential, providing extra information but not changing the meaning of the sentence, a comma is used to set it off.