He had plenty of feedback and plenty of time to mitigate this issue, but he can be stubborn.
句意：他有很多的反应时间去减轻这个问题，但他很固执。mitigate使缓和，使减轻。alleviate减 轻；缓和。shorten缩短；变短。increase增加；增长。revise修订；修正。A选项意义最为接近，故选A。