The police questioned each of the witnesses present one by one.
Tips
usage
挨个 (āigè) is synonymous with 逐一 (zhúyī) and 一个一个 (yīgè yīgè), but more colloquial. The 挨 here is pronounced āi (first tone), meaning 'next to / in sequence', not ái (second tone, meaning to suffer).
