What I wanted to know was when and where the meeting.（ ）A. was holdingB. had heldC. was to holdD. was to be held

步骤 1：分析句子结构
句子的主干是"What I wanted to know was when and where the meeting."，其中"What I wanted to know"是主语从句，"was"是系动词，"when and where the meeting"是表语从句。
步骤 2：确定时态和语态
根据句意，"the meeting"和"hold"之间是被动关系，因此需要使用被动语态。同时，根据语境，这里表示的是过去将来时，即在过去的某个时间点，会议将要被安排在何时何地举行。
步骤 3：选择正确的选项
A. was holding：表示过去进行时，不符合语境。
B. had held：表示过去完成时，不符合语境。
C. was to hold：表示过去将来时，但主语和谓语之间是主动关系，不符合语境。
D. was to be held：表示过去将来时的被动语态，符合语境。