Blank (i): B. distinguish
- Why? The sentence contrasts the temperaments of the two artists (Palmer and Frazer), not the quality of their work. While they might be excellent artists (hence "difficult to critique" or "evaluate"), the key is that even experts find it hard to tell them apart. The final part of the sentence proves this by listing their contrasting personalities, not their identical art. The core idea is about separating the two individuals.

Blank (ii): E. difference
- Why? The third phrase lists two contrasting temperaments: "Palmer was reserved and courteous, Frazer..." This clearly shows that their personalities were not the same. Therefore, the phrase is revealing a "surprising difference" in how they behave, which contrasts with the first phrase where they are hard to distinguish based on their work alone.

Blank (iii): G. choleric
- Why? This word forms the direct contrast with "reserved and courteous." Let's look at the definitions:
- G. choleric: easily angered, irritable, short-tempered. This fits perfectly as an opposite to "courteous."
- H. tractable: easily controlled or influenced; docile. This is too similar to "reserved and courteous."
- I. phlegmatic: calm and emotionless; stoic. This is also too similar to "reserved."
- Since the sentence requires a word that opposes Palmer's courteous nature, "choleric" is the only logical fit.

Final Complete Sentence:
This recent evaluation of two artists whose works even experts find difficult to (i) distinguish reveals a surprising (ii) difference in their temperaments: Palmer was reserved and courteous, Frazer (iii) choleric and boastful.