Here’s a little quiz I made earlier for a German student who was preparing for the TOEFL. It covers relative clauses, subsidiary clauses, and sentence comments.
https://www.opinionstage.com/api/v1/widgets/910654/iframe
I’ve also written a full article on comma usage, here:
(Cover photo: Marta Branco, on Pexels)
Englishin3d 