German prosecutors expanded the number of employees under investigation to 17, though they have yet to find firm evidence that senior executives knew about the rigged software in diesel cars that yielded false test readings. 

请问句中的两个 that 分别引导什么从句？

【翻译】德国检察官把被调查的雇员的人数扩大至17人，虽然他们还没有找到确凿的证据，表明高级管理人员了解柴油车中产生错误测试数据的操纵软件。

【分析】第一个that 从句that senior executives knew about the rigged software in diesel cars that yielded false test readings，是evidence的同位语从句，that是引导词，无实际意义。

第二个that 从句that yielded false test readings，是定语从句，修饰diesel cars。that是关系代词，指代diesel cars，而且在从句中作主语。

【详细分析】

1. expand the number to 17：把数字扩大到17；在数字后有一个定语of employees under investigation：被调查的雇员的；under investigation又作定语修饰employees。

2. have yet to do...：“还需要去做”，引申为“还没做到”。

3. firm evidence：确凿的证据。evidence之后经常跟同位语从句，如：The police have evidence that the killer was a woman. （警察有证据证明，杀人犯是个妇女。）

4. know about：了解

5. rigged software：被操纵的软件

6. yield false test readings：产生错误的测试数据。