The manager, _____ his factory's products were poor in quality, decided to give his workers further training.A. knowingB. knownC. to knowD. being known

步骤 1：分析句子结构
句子的主语是 "The manager"，谓语是 "decided"，宾语是 "to give his workers further training"。逗号后的部分是插入语，用来补充说明主语的状态或动作。

步骤 2：理解插入语的含义
插入语 "_____ his factory's products were poor in quality" 描述了经理知道工厂产品品质差的情况。因此，插入语应该表示经理知道这个事实。

步骤 3：选择正确的非谓语动词形式
A. knowing：表示主动和正在进行的动作，符合经理知道工厂产品品质差的情况。
B. known：表示被动和完成的动作，不符合语境。
C. to know：表示目的，不符合语境。
D. being known：表示被动和正在进行的动作，不符合语境。