Question

which sentence contains a nonrestrictive clause and is punctuated correctly?
the teacher packed picnic lunches for all the students—which they loved—and ate lunch outside with them all recess.
the teacher packed picnic lunches for all the students which they loved—and ate lunch outside with them at recess.
the teacher packed picnic lunches (for all the students) which they loved and ate lunch outside with them at recess.
the teacher packed picnic lunches for all the students which they loved and ate lunch outside with them (at recess).

Explanation:

A nonrestrictive clause provides extra, non - essential information and is set off by punctuation (like dashes or commas). In the first option, “which they loved” is a nonrestrictive clause set off by em dashes, and the overall punctuation is correct. The other options either lack proper punctuation for the nonrestrictive clause or misplace punctuation.

Answer:

The teacher packed picnic lunches for all the students—which they loved—and ate lunch outside with them at recess.