Warning that terrorists remain determined to strike the country, senior government officials urged citizens to remain vigilant and report suspicious behavior, taking actions necessary to speed up the recovery from an economic catastrophe should terrorists succeed in launching an attack.

• A. to remain vigilant and report suspicious behavior, taking actions necessary to speed up the recovery from an economic catastrophe
• B. to remain vigilant, reporting suspicious behavior and take actions to speed up the recovery from an economic catastrophe
• C. to be remaining vigilant, reporting suspicious behavior, and taking actions necessary to speed up the recovery from an economic catastroph
• D. to remain vigilant, report suspicious behavior, and take actions to speed up the recovery from an economic catastrophe