In 1886, what did the U.S. Supreme Court rule in Wabash, St. Louis, an

In 1886, what did the U.S. Supreme Court rule in Wabash, St. Louis, and Pacific Railway v Illinois?

(a) Only the federal government could regulate commerce across states.
(b) Only the states had the right to regulate commerce across states.
(c) Neither the federal or state governments had the right to regulate across states.
(d) Railroads were not subject to any government regulation, state or federal.

ANSWER

(a)