is vs are

The answer is 'is'.

Why is it 'is', please? Thanks.

Because it 'is'.

There should be a reason for "is". If you cannot explain, let's leave it to another user, please.

Then 'Google' it.
Takes 6.5 seconds.

You asked for the answer, not the reason why.

Efforts are. Mark, how did you get "is"

The efforts of Nichiren and his followers to have all the people in the country of Japan embrace the Lotus Sutra is/are the work of the envoy of Bodhisattva Jōgyō.”

It may help to cut out all the words that are not necessary to resolve the question. They are shown in red.

The result:

The efforts of Nichiren is/are the work of the envoy of Bodhisattva Jōgyō.

Subject-verb agreement: basic rule. A singular subject takes a singular verb, whereas a plural subject takes a plural verb.

The verb form would be 'is' if the subject is singular, and would be 'are' if the usbject is plural.

Is 'efforts' singular or plural?

Since Googling this phrase gets few if any identical or even similar hits, I'd go plural

Thanks, Tes yeux noirs and dalehileman.