这次袭击的动机是什么？

What was the ___motivation for the attack?

虽然金钱是主要动机，对许多人来说，工作是为了谋生，我遇到过许多人为了获得相关经验而自愿工作或赚更少的钱。

Although money is the main ___motivation, for many people, to work I have come across many people who have worked voluntarily or for less money to gain relevant experience.

理解他行为背后的动机对调查至关重要。

Understanding the underlying ___motivation behind his actions was crucial for the investigation.