To complete the cause and effect table, we need to find a suitable cause that leads to the effect "Companies began to prioritize advertising and use the services of professional advertising firms."
The most appropriate cause from the responses provided would be:
Cause: The new urban working population had more time and money to spend on shopping.
Effect: Companies began to prioritize advertising and use the services of professional advertising firms.
This cause suggests that as more people moved to urban areas for work, they had disposable income and leisure time, leading companies to recognize the need for advertising to attract consumers effectively.