Final answer:
The correct revision to sentence 5 is option B, which includes 'however', a transition word that introduces a contrasting idea regarding workers needing new skills in a changing workforce.
Step-by-step explanation:
The most effective way to revise sentence 5 to include a transition word or phrase is by selecting an option that best introduces the information about workers needing to gain new skills in the context of a changing workforce. Given that the previous sentences indicate a shift in workforce dynamics due to automation, a transition that implies consequence or conditionality is suitable.
Therefore, the correct revision to sentence 5 with a transition word would be: B. However, it will require some workers to gain new skills to meet the demands of a changing workforce. The word 'however' signifies a contrast or a possible challenge that arises from the previous statement, which is appropriate as sentence 4 talks about the positive potential for workers in high-skill professions, while sentence 5 mentions the need for some workers to adapt.