Question

Select the sentence that is punctuated correctly.

Answer 1

B. 
Unemployment is high in many fields, but there are jobs available in telecommunications.


A comma is used when it is placed after the end of one independent clause and the beginning of another which follows one such clause. The two independent clauses must be joined with words known as co-ordinating conjunctions. Examples of such words are, but, and,or so etc. 
In this sentence but is used, preceded by a comma so it is the right one.

Answer 2

B. Unemployment is high in many fields, but there are jobs available in telecommunications. There shouldn't be commas used when there's no coordinating conjunctions. There needs to be a semicolon in c for it to work