Forms 8a, 8c1, 8c2. Past Perfect vs Past Perfect Continuous

Practicing Past Perfect:

https://engelsklaslokaal.nl/en/english-grammar-exercises/one-english-verb-form/past-perfect/;
Practicing Past Perfect Continuous/Progressive:
https://engelsklaslokaal.nl/en/english-grammar-exercises/one-english-verb-form/past-perfect-continuous/;
Practicing Past Perfect vs Past Perfect Continuous:
https://elt.oup.com/student/solutions/upperint/grammar/grammar_02_022e?cc=lt&selLanguage=en;
https://speakspeak.com/english-grammar-exercises/upper-intermediate/past-perfect-simple-vs-past-perfect-continuous;
http://www.tinyteflteacher.co.uk/learning-english/grammar/exercises/past-perfect-2.html;
https://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-9553.php;
https://www.englishpage.com/verbpage/verbs13.htm.
QUIZ:
https://www.e-grammar.org/past-perfect-simple-continuous/test1-exercise1/.