Question

political parties are important in the us congress, because party affiliation
determines which new laws must be written.
allows for disagreements to be settled quickly.
decides the importance of various committees.
shapes the debate and controls legislative agenda.

Explanation:

In the US Congress, political parties play a key role in setting the legislative agenda (e.g., prioritizing bills) and structuring debates along party lines. Other options are incorrect: no single entity dictates which laws "must be written"; disagreements are not always settled quickly; committee importance is not solely decided by party affiliation.

Answer:

D. shapes the debate and controls legislative agenda.