They planned to hold a grand party to ________ their parents’ diamond wedding anniversary as a rewar

They planned to hold a grand party to ________ their parents’ diamond wedding anniversary as a reward for bringing them up.
A. congratulate B. memorize C. observe D. guarantee
【答案】C
【解析】
【详解】考查动词词义辨析。他们计划举办一个盛大的派对来庆祝他们父母的钻石结婚纪念日，以此作为抚养他们长大成人的回报。A. congratulate祝贺；B. memorize纪念；C. observe庆祝；D. guarantee保证。通过前文a grand party(盛大的派对)以及their parents’ diamond wedding anniversary 可知这里讲的是要庆祝父母的结婚纪念日，所以用observe(庆祝)来满足句意。故此题选C。