In each of the sentences below, a phrase that supports the main clause of the statement but should be distinct from it lacks an essential element that identifies it as a subordinate clause: a comma separating it from the main clause, thus obscuring the subordinate clause’s function. A discussion, followed by a revision, explains the solution to each sentence.
1. A hillside above the highway gave way showering the roadway with rocks.
“Showering the roadway with rocks” is a subordinate clause describing the consequence of the hillside giving way, so the phrase should be set off from the main clause with a comma: “A hillside above the highway gave way, showering the roadway with rocks.”
2. The only way you survive is you continuously transform into something else.
The transition from is to you seems awkward because there’s no grammatical continuity; in proper speech or writing, one simply does not use those two words consecutively. The solution? Because “The only way you survive is” is a subordinate clause, set it off from the main clause with a comma: “The only way you survive is, you continuously transform into something else.” Alternatively, insert the transitional pronoun that between the words, converting the subordinate clause into an integral part of the main (and only) clause: “The only way you survive is that you continuously transform into something else.” (Or revise the sentence to “The only way to survive is to continuously transform into something else.”)
3. Product defects that create a public health hazard will eventually be exposed to the light of day in the public arena and, when they are, the company pays the price.
At first glance, this sentence may seem correct: An apparent parenthetical, “when they are,” is introduced into the sentence after the conjunction, seemingly modifying the phrase “the company pays the price.” But that concluding phrase is an independent clause—a grammatically complete statement that could stand on its own as a separate sentence—and “and when they are” is not a parenthetical, but a subordinate clause associated with it.
Therefore, a comma should precede, not follow, the conjunction and, separating the two independent clauses. However, the second comma remains where it is to separate the clause subordinate to the second main clause: “Product defects that create a public health hazard will eventually be exposed to the light of day in the public arena, and when they are, the company pays the price.” (“When they are” may appear to serve both as a subordinate clause and as a parenthesis, but it is essential to the sentence, pertaining to the catalyst for the company’s comeuppance, so it cannot function in the latter role.)