The Fort Hood, Boston Marathon, and San Bernardino attacks show that ______.

The selected answer highlights the reality that homegrown terrorists, or individuals who, while not necessarily affiliated with a specific foreign terrorist organization, adopt extremist ideologies from such groups, can blend into societies undetected until they carry out their attacks. This phenomenon has been observed in various incidents, such as those mentioned in the question.

In the case of the Fort Hood shooting, the perpetrator was a U.S. Army psychiatrist who had been radicalized but was able to live and work within the military community without raising significant alarms, illustrating that individuals with extremist views can maintain normal lives and gain trust within communities. Similarly, the Boston Marathon bombing involved the Tsarnaev brothers, who were U.S. residents but influenced by radical jihadist propaganda. The San Bernardino attack saw a married couple, both of whom were U.S. citizens, carrying out an attack inspired by extremist beliefs, indicating their ability to live among the civilian population undetected until the time of their attack.

The context of the other options emphasizes a misunderstanding of the nature of threats faced. The assertion that terrorists cannot remain hidden fails to reflect the reality of how individuals can plan and execute attacks over extended periods while remaining inconspicuous. The idea that security measures are effective against such attacks overlooks the