Which sentence is correctly punctuated.
1. The cost, and size of computers are decreasing, almost as rapidly as processing power is increasing.
2. Database management systems were originally large, unwieldly, and ready to use.
3. A factory closing means the community loses jobs tax revenues and retail sales.
4. An operating system is the set of instructions, that directs the overall operations of the computer.
1. comma after "cost" isn't needed
2. series -- http://grammar.ccc.commnet.edu/grammar/commas.htm
3. series -- http://grammar.ccc.commnet.edu/grammar/commas.htm
4. comma after "instructions" isn't needed
So you decide between 2 and 3.
=)
The correctly punctuated sentence is:
3. A factory closing means the community loses jobs, tax revenues, and retail sales.
In this sentence, commas are used to separate the series of items: jobs, tax revenues, and retail sales. This is known as the rule of the serial comma or the Oxford comma. It is generally recommended to use a comma before the coordinating conjunction (in this case, "and") when separating three or more items in a series. This helps to avoid ambiguity and clarify the meaning of the sentence. In this case, it is clear that the community loses three separate things: jobs, tax revenues, and retail sales.
For more information and examples of this punctuation rule, you can refer to the website provided: http://grammar.ccc.commnet.edu/grammar/commas.htm