Answer:
I personally feel all the options allow a good evaluation in the annotation process in an author's piece, but I'll list below what I personally think is the best, but I believe this question is opinion-based.
1. How has the author supported the main ideas in the text?
The main ideas and the technique the author uses to support their research or opinions are major key elements in annotating and comprehending the text.
2. What important ideas does the text include?
Thinking of all the ideas presented in the text and how they are important to the overall piece of work is important, relates to #1 though.
3. How effective is the text structure in sharing the important ideas?
Text structure! Many may overlook this but verses, poems, and even dialogue are all shown in different formats of text structures. It's important to view these things.
These are good but...
What opinions are conveyed within the text?
What text structures does the author use?
I believe they kinda relate to the one's listed above.