Mortise locks are installed by cutting a pocket into the edge of the door so the lock body sits recessed inside the door, with a faceplate flush with the edge. That recessed, embedded installation is what defines a mortise lock. Because of that setup, the statement about being mounted on the surface is not a characteristic of mortise locks. They’re designed to live inside the door, not on its surface. The other statements fit standard practice: being recessed into the door is exactly how they’re installed; they’re used on doors that need a robust latch and often work with a door knob or lever to operate that latch; and they’re commonly found on building entrance doors where extra security and durability are desirable.

Potency refers to the amount of drug needed to produce a given level of response. On a dose–response curve, it’s about where the curve sits along the dose axis: a more potent drug reaches the same level of effect at a lower dose, so its curve is shifted to the left. The common way we quantify this is by EC50, the concentration that yields 50% of the maximal effect. This concept helps compare drugs that may achieve the same maximum effect (efficacy) but require different amounts to get there. The maximal effect a drug can produce is called its efficacy, which is about the height of the curve, not the dose needed to reach it. The other options refer to different ideas: onset of action is about how quickly the drug starts working, and selectivity describes preference for a receptor subtype.

Electromechanical locks move their bolt or solenoid using electrical energy, so they must have a power source. The usual ways are internal batteries that keep the lock powered without being wired to building power, or energy that’s generated or captured during operation (self-powered) so the lock can function without a constant external power supply. Some installations do connect to building power (line-powered), but that adds wiring and is less common for standalone devices. Solar power exists in some outdoor or low-power cases, but it’s not the standard approach. Hydraulic-actuated systems aren’t typical for these locks, since hydraulics add fluid plumbing and pressure rather than the electrical actuation used in electromechanical models. So the most accurate description is that these locks are powered by internal batteries or by energy harvested during use.

To change a combination, you need access to the lock’s internal change mechanism. That access is only available when the lock is open. In the open position, the bolt is retracted and the internal wheels or pins can be moved to set a new combination. If the lock is closed or locked, the internal components are secured, so you can’t perform the reset. A half-open state still doesn’t expose the change mechanism, so it won’t work for reprogramming. Disabled isn’t a normal state for changing a combination. So, open is the correct position because it provides access to the parts you must adjust to set a new code.