Which sentence should replace the following incorrect sentence? "This door to remain unlocked when occupied."

The sentence "This door will remain unlocked when the office is occupied" is correct because it uses the future tense verb "will remain," indicating an ongoing action that will occur under specific conditions. The phrase effectively communicates that there is an intention for the door to stay unlocked, which aligns with the intended meaning of the original statement. The inclusion of "when the office is occupied" provides clarity about the context in which the door remains unlocked, making the sentence clear and grammatically correct.

In contrast, other options either introduce grammatical errors or do not maintain the original intent. For instance, another option uses a verb form that does not align with standard English grammar, resulting in a lack of clarity. Additionally, options like "This office must have the door unlocked at all times" alter the original meaning, implying a different scenario by suggesting a perpetual state rather than a conditional one based on occupation.