参考答案：A

解析：形容词辨析。felt cheap感到惭愧，觉得身体不舒服；在此cheap是形容词，表示“可鄙的，低劣的”。A．felt inferior and ashamed感到自卑和羞愧；B．felt not worthwhile of doing something感到做某事不值得；C．felt bad about doing something对做某事感到抱歉、不安；D．felt unhappy about doing something对做某事感到不满。