Please help ASAP ! Which historical event BEST demonstrates the operation of checks and balances?

A) The Senate approved the appointment of Clarence Thomas to the Supreme Court.

B) South Carolina seceded from the Union over the issues of slavery and States rights.

C) President George Washington used the Army to suppress a tax rebellion by Pennsylvania farmers.

D) President Dwight D. Eisenhower sent Federal troops to enforce the integration of public schools in Little Rock, Arkansas.

Asubject in a clinical research trial experiences a serious, unanticipated adverse drug experience. how should the investigator proceed, with respect to the irb, after the discovery of the adverse event occurrence? a. do not report the adverse drug experience to the irb since it is a common adverse experience. b. report the adverse drug experience to the irb only if there are several other occurrences. c. report the adverse drug experience as part of the continuing review report. d. report the adverse drug experience in a timely manner, in keeping with the irb's policies and procedures, using the forms or the mechanism provided by the irb