JFinal ActiveRecordException: 无效的列索引

代码：

Db.update("delete from T_Xabc where ID= ‘?‘","9900");

现象：

com.jfinal.plugin.activerecord.ActiveRecordException: java.sql.SQLException: 无效的列索引
	at com.jfinal.plugin.activerecord.DbPro.update(DbPro.java:279)
	at com.jfinal.plugin.activerecord.Db.update(Db.java:206)

正确代码：

Db.update("delete from T_Zabc where ID = ? ","9900");