Final answer:
By combining the given sentences into one complex sentence, the result is b) 'There is a mixture of cultures that has worked to form ethnically rich cultures in both countries,' effectively conveying the idea of cultural diversity leading to vibrant cultures.
Step-by-step explanation:
To combine the sentences 'There is a mixture of cultures' and b)'The mixture has worked to form something',
as well as 'There is a mixture of cultures' and 'The result is ethnically rich cultures in both countries' into one complex sentence, you could use an appropriate subordinating conjunction.
A complex sentence can express multiple ideas and maintain clarity by using subordinate clauses which add detail to the main clause. Here's how you could structure the complex sentence:
There is a mixture of cultures that has worked to form ethnically rich cultures in both countries.