窗户没有关紧，感觉不太安全。

The window felt ___insecure because it wasn't closed properly.

请不要在未加密的网络上传输敏感信息。

Please don't send sensitive data over an ___insecure network.

他在新学校的第一天感到很不自信。

He felt ___insecure on his first day at the new school.