选词填空 — 英语选择题

选词填空（先判断空格所缺成分的词性，再结合语义选择）。句子：The annual survey ______ that the number of students studying abroad had risen steadily over the past five years. 空格处应填入的词性及正确形式为：A. 名词单数 B. 动词过去式 C. 形容词 D. 名词复数