"Ils choisiront un paragraphe et ils le liront."

Translation: They will choose a paragraph and they will read it.

[cricri811231]

why both sentences are accepted ;

they will choose the paragraph and they read it or they will choose the paragraph and they will read it ?

[Jojo553168]

... and why is the paragraph accepted as a translation of un paragraphe ?

[GraemeSarg]

I can't explain the definite article but the former is probably an unintended side effect of (correctly) accepting "They will choose a paragraph and read it.".