How do you know if its a compound or a simple sentence

A simple sentence has a subject and a verb. Ex: Bart ran. A compound sentence is TWO simple sentences combined. Ex: Bart ran, while eating cheese. It combines an independent clause and a dependent clause. An independent clause is a simple sentence.

i have heard the mermaids singing, each to each.

i do not think they will sing to me

the correct answers are:

c. “never in the history of his people had a man married a woman who spoke a different tongue.”

d. “‘it has never been heard,’ was the verdict of an old man speaking a few weeks later.”

e. “this man had come with others to commiserate with okeke.”