Hi Lingolo, Following is my "version":
Share prices of Chinese steelmakers have been bullish. ==> Many steelmakers : many various prices
The price of TVs will drop. ==> refer to genaral televisions
The company's operating profit was stellar. ==> It depends on how many company you're talking about.
Next quarter earnings forecast remains upbeat. ==> It's "earnings" because it's always flural, and it's "remains" because "forecast" is single noun
The factory will be full of operations next year. ==> This sentence sounds awkward to me. How about these: " The factory will start many operations next year" or "The factory is going to extend current operations."
Oil refining and petrochemical business are expected to do well. Or: "Oil refineries and petrochemical businesses are expected to do well."
Jack and Diane love each other. ==> Jack + Jane = plural