It's always a mistake to think of grammar as involving commas and words following them. Grammar is clauses and phrases and predicates; there are no commas in language, only in writing.
In this case, there are two clauses:
- ((Eric's) psychology class) was different from the other classes (that) (Eric) had taken
- (Eric) was unhappy with ((Eric's) psychology class)
The pieces in parentheses are either deletable markers (like relative that) or noun phrases that can be replaced by pronouns (like he, his, and it) in the appropriate circumstances.
The problem is what the appropriate circumstances are for pronominalization, and that's what this question tests.
Pronouns always refer to someone or something that's obvious in context. When the context consists of only one sentence, the word denoting the person or thing (called the "antecedent") must be in the same sentence as the pronoun in order to be obvious.
But not just anywhere in that sentence. As the word antecedent (Latin for 'going before') suggests, normally the antecedent is spoken before the pronoun.
- He likes Eric's psychology class
is a perfectly good sentence, provided he doesn't refer to Eric; otherwise it's garbage. Switch them and it's fine. But this sentence has two clauses: sentence 2 is the main clause, and sentence 1 is a subordinate clause; this makes a difference for pronoun usage.
If the antecedent is in the main clause, and the pronoun is in a clause subordinate to the main clause, then a pronoun can come before its antecedent. For example, consider some simpler sentences:
- Before Marilyn became president I knew her.
- I knew Marilyn before she became president.
- Before she became president I knew Marilyn.
- *I knew her before Marilyn became president.
The first three are fine; in the first two, the antecedent (Marilyn) comes before the pronoun (her or she). In the third, the antecedent is in the main clause but the pronoun is in a subordinate clause, so even though the pronoun precedes its antecedent, it's OK. That's the same structure as the SAT sentence, and that's why the answer says there is no mistake.
But the fourth one is ungrammatical (that's what the asterisk indicates), because the pronoun is in the main clause and it precedes its antecedent, which is in a subordinate clause. So the SAT question tests whether you know the rule that distinguishes the third OK case from the fourth ungrammatical case.
(All) that much is a quantifier, but more importantly it's an idiomatic Negative Polarity Item.
That is, it can only occur felicitously within the scope of a negative trigger.
Like didn’t. Notice that you can certainly say
- I didn't understand all that much of what she said.
but you can't say
- *I understood all that much of what she said.
because there is no negative trigger present.
In the appropriate negative context, it means, basically, not much at all
- I doubt he enjoyed all that much of the play.
- It isn't as if she weighed all that much.
And it can also be used with other quantifiers and qualifiers besides much:
- She isn't all that gorgeous.
- If it's all that important, why don't we hear more about it?
Best Answer
It is only different in being a bit wordy, which might be done for emphasis. One could just as well say "you must gain that which you lack". All correct, all same meaning, different sound.
It's probably part of a speech pattern for a particular character. Often in movies a character is partly defined by subtle differences in how he/she uses language.