whom were injured …是一个定语从句，句子一定要有主语谓语。这里whom相当于主语，were injured是谓语。因为这里是被动语态，单独的injured不能作谓语。
看这个句子：A man (主语)injured in the accident (定语)is lying (谓语)on the ground.句中injured作定语修饰主语，不能用be injured.此处injured也不是动词，而是形容词。
总之主语后面一定要加上am,is,are,或者have,has,等时，说明其后的动词作谓语。
