How does the United States judicial system differ from those of most other countries?

a. The United States has both federal and state courts, whereas most countries have a single national judiciary.
b. The United States has both federal and state courts, whereas most countries have decentralized judicial systems.
c. Unlike most other countries, the United States offers justices life tenure.
d. Unlike most other countries, the United States grants the judicial branch the power of judicial review.

a