the police know the killer's identity they are getting close to catching him. A. Even if

问题补充：

the police know the killers identity, they are getting close to catching him.

A. Even if

B. Although

C. Now that

D. As long as

答案：

A. Even if

B. Although

(答案→)C. Now that

D. As long as

解析：根据语境they are getting close to catching him可知应该用Now that。句子意思是“警方既已掌握了这名杀手的身份，要将他逮捕归案也就指日可待了。”