Final answer:
The most common political system today that prevents one party from controlling the government is a multiparty system.
Step-by-step explanation:
The most common political system today that prevents one party from controlling the government is a multiparty system. In this system, many political parties hold seats in the legislature, and parties often need to join together in coalitions to create a majority. A good example of this is the United Kingdom, where the Conservative Party and the Labour Party have historically dominated, but the emergence of other parties has made it look more like a multiparty system.