加倍

double; redouble; doubly

警惕

alert; be vigilant; be on guard against; be wary; be watchful; be alert; be cautious; be on the lookout; keep one's eyes peeled; stand guard against; watch out for; keep a weather eye on; guard against; vigilant; watchful; wary; on guard; cautious; circumspect; vigilance; alertness; caution; on the qui vive