Explanation:

- Probe: This word means to investigate or explore something thoroughly. It implies an in-depth examination or inquiry.

- Option 1, Search: This involves looking for something or someone, usually in a thorough way. While it is close, it lacks the investigative depth 'probe' suggests.

- Option 2, Motivate: Means to inspire or encourage someone to act in a certain way. This is unrelated to 'probe.'

- Option 3, Invite: Refers to asking someone to attend or participate in something. It’s not related to probing.

- Option 4, Push: Generally means to apply force to move something. It does not align with the idea of investigation.

- ?? Correct Answer: Option: 1, Search