The correct answer is B. Precedents set by the Supreme Court with Marshall as Chief Justice were important because they influenced the legal and economic systems in the United States.
When the Founding Fathers of the United States made the Constitution, they didn't write which had to be the exact role and functions of the Supreme Court. That task was the work of John Marshall, its president between 1801 and 1835.
Marshall managed to turn the Supreme Court into the highest interpreter of the Constitution and made the doctrine of judicial review accepted by both the legislature and the executive, placing the judicial branch on an equal footing with them, a concept that today is part of the constitutional architecture of all the democratic countries of the world.