Which of the following is a passive measure to protect against laser exposure?

Taking cover is considered a passive measure to protect against laser exposure because it involves using the environment to shield oneself from potential harm. This approach does not require active engagement or immediate response but instead relies on finding a safe location that can block or minimize exposure to the laser.

In the context of aviation, passive measures are those that do not involve direct interaction with the threat but instead aim to provide a safeguard through physical barriers or by altering one's position effectively. By taking cover, a crew member can reduce the chances of harmful laser exposure without needing to respond to the laser threat actively.

Other options, such as using monocular optics or wearing protective goggles, can be seen as more direct methods of actively mitigating laser exposure but do not fit the definition of passive measures in this context. Evasive maneuvers, on the other hand, represent an active response to a perceived threat rather than a way to shield oneself passively.