Explanation
Correct answer: B.
Choice B is the best answer. The convention being tested is the coordination of main clauses within a sentence. This choice uses a semicolon in a conventional way to join the first main clause (“In 2004…sampler”) and the second main clause (“in 2014…pillars”).
Why the other choices are wrong
Choice A
Choice A is incorrect because it results in a comma splice. Without a conjunction following it, a comma can’t be used in this way to join two main clauses. The word “later” is an adverb and cannot be used to join two main clauses unless it is preceded by a conjunction.
Choice C
Choice C is incorrect because it results in a comma splice. Without a conjunction following it, a comma can’t be used in this way to join two main clauses.
Choice D
Choice D is incorrect because it results in a comma splice. Without a conjunction following it, a comma can’t be used in this way to join two main clauses. The word “later” is an adverb and cannot be used to join two main clauses unless it is preceded by a conjunction.