What term refers to a set of behaviors or beliefs that is rigidly conventional?

The term that refers to a set of behaviors or beliefs that is rigidly conventional is "ossified." This word originates from the biological process of ossification, where tissue becomes hardened or bony. In a metaphorical sense, when describing beliefs or behaviors as ossified, it implies that they have become so entrenched or rigid that they are resistant to change or evolution. Such beliefs are often out of touch with current realities and can hinder adaptability and innovation.

The other choices do not convey this meaning. "Luculent" refers to clarity and brightness, typically associated with speech or writing. "Macerate" means to soften or break down, particularly in a liquid context, which is opposite to the idea of being rigid. "Lubricious" denotes something that is slippery or, in some contexts, lewd or salacious, and does not relate to the idea of rigidity or conventionality. Hence, ossified is the appropriate choice for describing inflexible beliefs or behaviors.