单选题 Tom is always lack of self-confidence. His ______ character called him to miss many golden opportunities.

【正确答案】 A

【答案解析】[解析] 形容词词义辨析。根据句中miss many golden opportunities提供的信息，空格应填入与lack of self-confidence意思相近的形容词。选项中，diffident(羞怯的；缺乏自信的)符合句意。故答案为A。