What are right pronouns to use in the following sentences? Please give some explanations too.
1. If I were (she, her), I would accept the offer.
2. Who is younger, you or (I, me)?
3. Everybody seems to know more than (I, me).
Thank you for being very helpful.
1. Either 'she' or 'her'. Note, 'were' links the subject "I" with its complement "she":
is Subject Complement
Speakers who use the informal structure do so based on a variation of a grammatical rule: the word that directly follows the verb is the object of the verb, and hence use an object pronoun. The problem, however, is that the verb To Be is an exception to the rule: It takes two subject (pro)nouns, one before and one after. I am she. / I am he.
2. Again, 'is', a linking verb, joins the Subject "Who" with it's complement 'younger'. Who = You or I.
am younger. Who
3a. to know
more than I know
3b. to know
more than I. (OK; formal)
3c. to know
more than me. (OK; informal)
In 3a. "know" is redundant, so in 3b. "know" is omitted, but it's still implied, and so its subject "I" remains; in 3c. "I" is replaced by "me" because the verb is not overt (i.e., spoken/written).
Speakers who use the structure 'than me' do so based on a grammatical rule: If there's a verb after "than", use a subject pronoun; if there isn't a verb after "than", use an object pronoun.
All the best,