Exactly. It's a compound predicate, and just like in the case of a compound subject, e.g., "Anna and I are tall" or "Bob and Joe are short" you would (or at least could) use the plural for agreement. You wouldn't say "Bob and Joe is short". I don't have a problem with "there was" being accepted as it IS often (maybe more often) used, but "there were" shouldn't be rejected.
If you are concerned with the difference in number (singular versus plural), this is not necessarily a problem -- a plural verb is correct. AndreasWitnstein draws our attention (below) to the distinction between the mass noun (tension) and the count noun (arrests). In view of this I think using two verbs is a better solution in this example.
My bad. Varios could have meaning of 'some' and in this sense it should be placed in front of a noun as any other limiting adjective, but does the word 'various' belong to the group of limiting adjectives? And how come vario has meaning of 'various' and varios does not?) Very weird.
That would certainly be more natural, but I think that Duolingo would not like to replace an adjective with a noun. John Ekegren further down tried "numerous", but it was not accepted as that would have been numeroso and it would not have solved the verb problem. Try reporting it and provide this link: https://dictionary.reverso.net/spanish-english/vario
I thought of switching it around to "There were several arrests and tension.", but again I didn't think that Duolingo would accept the answer switched around.
why not "muchas" if they want to say "many" or " a lot of". I used "assorted" and it was rejected even though it appeared in the glossary with "several" and "miscellaneous" and "assorted" as definitions of "varios". Neither "many" nor "a lot of" are I think good definitions of "varios' !
Good question. After all, you can say either “There was an apple and [there were] three oranges.” or “There were an apple & three oranges.”. The difference is that in the latter case, apples and oranges are both count nouns, so they can be counted together and take a plural verb. But ‘tension’ is a mass noun, so it can't be counted along with the arrests.
To my knowledge, two subjects joined by "and" ALWAYS require a plural verb. I had not heard of this stated rule that mass nouns and count nouns can't share the same verb, so I googled it. I did not turn the internet upside down, but none of the top few results say anything of this nature. Could AndreasWitnstein (or anyone else) point me to a relevant link if this is indeed a rule of English grammar that I've never learned?
I still maintain that "There were tension and several arrests" is correct and should be accepted. "There was. . ." is definitely incorrect. I'm fine with Duo accepting it, as it is very common to use "there was" when "there were" should be used, but "there were" certainly shouldn't be marked wrong.
Here you can think of "There was" or "There were" as showing the existence of the following things.
You could try reporting it, but I think Duolingo prefers "unos" for "some".