The lowest level of cognitive achievement is

Bloom's Taxonomy (1956) arranges cognitive learning outcomes into six hierarchical levels, ranked from the simplest mental operation to the most complex: knowledge, comprehension (understanding), application, analysis, synthesis, and evaluation. Each level requires the abilities of the level(s) below it, so a learner must be able to recall information before they can understand, apply, or analyse it.

1. Knowledge (level 1 of 6) — recalling or recognising previously learned facts, terms, and basic concepts, without any requirement to explain, use, or break them down.

2. Understanding / comprehension (level 2 of 6) — grasping the meaning of information well enough to explain it in one's own words; this presupposes that the material has already been recalled.

3. Application (level 3 of 6) — using learned rules, methods, or concepts to solve a new, concrete problem; this presupposes both recall and comprehension of the material.

4. Analysis (level 4 of 6) — breaking material into its component parts and examining the relationships between them; the most demanding of the four levels offered here.

Ordering the four offered levels by Bloom's standard hierarchy gives knowledge (1) < understanding (2) < application (3) < analysis (4), confirming knowledge as the lowest level of cognitive achievement among the options.