There is/ there are

https://dictionary.cambridge.org/es/gramatica/gramatica-britanica/there-is-there-s-and-there-are
http://www.ejerciciodeingles.com/cuando-usar-there-is-there-are/
http://www.saberingles.com.ar/curso/lesson05/04.html
https://madridingles.net/como-usar-there-is-there-are/
https://www.englisch-hilfen.de/en/exercises/various/there_is_there_are.htm
https://agendaweb.org/grammar/there_is_are-exercises.html