a) I would use "are". It does produce a sentence that is somewhat unwieldy, but appears to me to be grammatically correct.
b) I notice that the original poster has a Japanese flag - I've found generally that those who learn the language abroad are much better educated in the structure of the language than those who speak it as a first language. In countries with English (or American-English etc) as a first language, the use of grammar is often quite shocking and the language is used to get a point across and the actual correct use of grammar is often ignored. Double negatives being a good example of this ("I ain't got none"
c) Though I'd use "are", it sounds quite formal and I wouldn't be concerned if someone used "is" in conversation.
d) There appear to be very few (if any) Americans contributing to this topic...
e) Language is a fluid and ever changin thing. More so in recent times with the internet and the increasing Americanisation of the language. If we had this conversation again in 30 years, it is probably that either would be fine... Rules on grammar are being relaxed more and more each year. Is this a good thing? That's the real question...



