Answer:
B. Royalty there demanded protection from the sun, and people developed the umbrella for this purpose
Step-by-step explanation:
The most important thing to know here is the proper way to combine two independent or independent and dependent clause.
Now, answer A. uses "demanding" instead of "demanded". This makes the sentence hard to understand and slightly illogical.
Answer B. combines two independent clauses with a comma and conjunction "and" which is a proper way.
Answer C. has a dependent clause "which royalty demanded". When dependant clause comes after independent, it shouldn't be separated by a comma.
Answer D. is written in a complicated manner and doesn't make much sense.
So, in this particular case, answer B. seems to fit the best.