Lei Feng _____ always _____ of others when he ______ in the army.a.is,thinking,was b.was,thinking,is c.did,think,is d.wa

Lei Feng _____ always _____ of others when he ______ in the army.a.is,thinking,was b.was,thinking,is c.did,think,is d.was,thinking,was 为什么是D而不是B