What is the correct use of punctuation in this question?

Most bookstores stock the most common way people discover and start origami, being a kit

A) NO CHANGE
B) origami:
C) origami;
D) origami

We can eliminate the options A and C. A is not a correct use of a modifier. While C is not correct because we use a semi-colon in the case of two independent sentences. Most students chose D. But the correct answer is B. Why it is grammatically correct I don’t understand.