Designing a database for Reading Comprehension
1st things first:

Use TEXT for all character fields including small ones! In SQLite, VARCHAR is just TEXT behind the scenes anyway (same is true for PostgreSQL if ever you want to upgrade to a multi-user RDBMS).

Note on style (others may differ - but I know best! :-) ):

Use lower case for your identifiers (table and column names) and UPPER CASE for your SQL KEYWORDS (SELECT, FROM, ORDER BY... &amp;c.). Use underscores_to_separate_identifier_parts! Use singular names for identifiers - a table is a set anyway, so why pluralise it? If you have a problem with any of this, there are plenty of style guides (this one is good) out there, but if you choose a convention, then stick to it! This will make life much easier. Finally, make use of the comments facility - in SQLite, it's not great, but it's there! It's easier to just issue a CLI client command or SQL statement than go searching for docco!

This schema should get you started (you could add fields to these tables as appropriate for  your particular situation).

The Passage table:

CREATE TABLE passage
(
  passage_id INTEGER PRIMARY KEY, -- this will automatically auto increment
  passage_text TEXT NOT NULL, -- could check for a minimum length here!
  source_name TEXT NOT NULL, -- 
  ISBN TEXT, -- note, no NOT NULL - a URL doesn't have an ISBN for example
  author TEXT -- maybe author not known or it's an institutional website? 
  passage_date -- if known/applicable.. other stuff...
);


If you have multiple authors, you could have an author table and then a passage_author table as an associative entity (or joing table - there are other names - see Wiki). 

Question (each one refers to its own passage - that's what the FOREIGN KEYs are for!

CREATE TABLE question -- or quiz, but I'm keeping it singular!
(
  question_id INTEGER PRIMARY KEY,
  q_passage_id INTEGER NOT NULL,
  question_text TEXT,
  CONSTRAINT question_passage_fk FOREIGN KEY (q_passage_id) 
    REFERENCES passage (passage_id) -- meaningful names are very helpful in error messages!
);


Replies to the questions (each option refers to its own question and passage):

CREATE TABLE option
(
  option_id INTEGER PRIMARY KEY,
  o_passage_id INTEGER NOT NULL,
  o_question_id INTEGER NOT NULL,
  option_number TINYINT, -- CHECK here for &lt; 10?
  option_text TEXT NOT NULL,
  CONSTRAINT option_passage_fk FOREIGN KEY (o_passage_id) 
    REFERENCES passage (passage_id),
  CONSTRAINT option_question_fk FOREIGN KEY (o_question_id) 
    REFERENCES question (question_id),
);


All this is available here on a fiddle!