When you use a comma to join two independent clauses that can stand alone as sentences, you have created a(n).
A. adjective
B. fragment
C. compound word
D. comma splice

D comma splice

Explanation:

In most cases, joining two independent clauses(i.e., clauses that can stand alone as complete sentences) by a comma creates a comma splice.

i have heard the mermaids singing, each to each.

i do not think they will sing to me

the underline word is basically like a prepositional phrase.