Which of the Following Are Accurate Findings of Recent Studies

Which of the following are accurate findings of recent studies about the effectiveness of intervention activities?

A) Intervention is often effective for two weeks or less in reversing the direction of the trend of the exchange rate or reducing the speed of the trend.
B) The effectiveness of the intervention usually continues past the initial two-week period and can be observed in the trend for months to come.
C) Smaller interventions are usually more successful than larger interventions.
D) The interventions are usually more effective when exercised by individual monetary authorities rather than by two or more authorities intervening jointly.