be alert to

对…警惕(警觉，留神，注意等)

BBC, BBFC, BC, be, be (badly) in need of, be able to, be able to do, be about to, be about to do, be absorbed in, be abundant in, be accustomed to, be acquainted with, be addicted to, be adequate for, be affected with, be afraid, be afraid of doing sth., be afraid of sth.(sb.), be afraid to do sth., be alike to, be alive to, be all ears, be ashamed of, be ashamed to do, be assigned to do, be associated with, be astonished at, be at ease with, be at the end, be at war, be attached to, be attentive to, be available for, be available to, be aware of, be beneficial to, be better off, be blessed with, be blind to,