3. Relative clauses
Distinction:

Relative clauses with prepositions

Fixed prepositional phrases:
in which case
at which point
as a result of which
the result of which
since when
by when / by which time
all/some/several/… of which/whom
Whose → people and things
Where/When → in defining and non-defining clauses
Why → only defining clauses, after word reason
Whom → Animate antecedent + preposition =whom SVO
Coordinate relative clauses: relative pronoun refers back to entire main clause
Contact clause
Defining relative clause
Relative clause has to have own subject
Step by Step guide
Which element is repeated in both sentences?
Do we need defining or non-defining clause? Commas?
Which relative pronoun? Contact clause?
Delete underlined element and put relative pronoun in 2nd sentence in its proper place
Insert relative clause into main clause, comma if needed