Which Statement Is Accurate in Relation to the Contraction Stress

Which statement is accurate in relation to the contraction stress test (CST) ?

A) The CST sometimes uses vibroacoustic stimulation.
B) The CST is an invasive test no matter how contractions are stimulated.
C) The CST is considered negative if no late decelerations are observed with the contractions.
D) The CST is more effective than the nonstress test (NST) if the membranes have already been ruptured.