The sentences that are correctly punctuated are Sentences B, C, and D.
Sentence A is not correctly punctuated as it is a run-on sentence. Contrary to what the name “run-on sentence” implies, a run-on sentence is not a sentence that runs on with lots of words. It, for instance, is entirely possible for a grammatically correct sentence to have, even, over a hundred words as long as it is properly punctuated. In fact, a run-on sentence is a sentence this simply missing punctuation. For a sentence to be considered a run-on sentence the appropriate punctuation will be missing between two complete thoughts. That said, Sentence A has two complete thoughts, and they are as follows:
<em>Some workers train dogs to become service dogs for people who need assistance
</em>
<em>
others workers accompany the mobile spay and neuter project for inner-city pet owners
</em>
There are three ways to correct a run-on sentence.
1) You could use a period between the two complete thoughts:
<em>Some workers train dogs to become service dogs for people who need assistance</em><em>. </em><em>Other workers accompany the mobile spay and neuter project for inner-city pet owners.
</em>
2) You could use a semicolon between the two complete thoughts:
<em>Some workers train dogs to become service dogs for people who need assistance</em><em>; </em><em>other workers accompany the mobile spay and neuter project for inner-city pet owners.
</em>
3) You could use a comma/conjunction between the two complete thoughts:
<em>Some workers train dogs to become service dogs for people who need assistance</em><em>, and </em><em>other workers accompany the mobile spay and neuter project for inner-city pet owners.
</em>
