a) present perfect and past participle

Also see II-A-5-b-3) (supplementary:) present participle vs. past participle

Present Perfect tense
source: Crown Academy of English     2014年9月3/12日

The Present Perfect Tense
source: learnamericanenglish    2008-05-30

Present Perfect Tense
source: englishgrammarspot     2013-03-25
www.englishgrammarspot.com

PRESENT PERFECT
source: JenniferESL   2008-12-09

Present Perfect and Past Participle
source: Alan Nicholls    2009-11-12

How to use the Present Perfect tense
source: MrSkypelessons  2014-4-10
http://skype-lessons.com/

Present Perfect Tense in daily English Conversation - Using HAVE & HAS Correctly
source: Learn English with Let's Talk          2017年6月28日
http://www.learnex.in/present-perfect...

The Present Perfect Tense
source: mmmEnglish      2017年9月12日
the full transcript: https://www.mmmenglish.com/2017/09/13...

Present Perfect
source: Daily Dose of English   2011-05-10 
http://DailyDoseOfEnglish.com