Which adjective is used to describe something that seems true but might not actually be true?

The adjective "ostensible" is used to describe something that appears to be true, or is stated to be true, but may not actually be the case. It reflects a sense of superficiality or an outward appearance that can be misleading. For example, if someone claims to have a strong commitment to a cause, their ostensible dedication might mask a lack of genuine commitment underneath. This term captures the essence of something that is put forward as real or valid, yet is open to skepticism regarding its authenticity.

The other options do not convey the same nuanced meaning. "Luculent" refers to something that is clear or easily understood, "ossified" describes something that is rigid or inflexible, often in a metaphorical sense related to thoughts or systems, and "officious" denotes someone who is overly eager to volunteer services or offer unwanted advice, which lacks any connection to the idea of truth versus facade. Thus, "ostensible" is distinctly appropriate for indicating a semblance that may not align with reality.