求解： I am not familiar with the song — it’s the first time I have heard it _____. <?xml:namespace prefix="o" ns="urn:schemas-microsoft-com:office:office"></?xml:namespace>
A. sing B. to sing C. singing D. sung
分析语法成分，详细解析。
求大神帮助
求解： I am not familiar with the song — it’s the first time I have heard it _____. <?xml:namespace prefix="o" ns="urn:schemas-microsoft-com:office:office"></?xml:namespace>
A. sing B. to sing C. singing D. sung
分析语法成分，详细解析。
求大神帮助
