#decidability

Question 1: Single choice

mediumAI-checkedKnowledge Representation & Reasoning

In propositional logic a complete truth table decides whether a sentence is a tautology. Why is there no analogous table-based test for validity in first-order logic?

A sentence has infinitely many interpretations, which cannot be checked one by one1
One counter-interpretation is not enough to show a sentence is not a validity2
An FOL sentence can be true in one interpretation and false in another one3
With $n$ predicates a truth table would need $2^n$ rows, too many to write4

Timed test