Both, either, neither, all take the noun as the subject, and the predicate is singular or plural?
When both is followed by a noun as the subject, the predicate is regarded as plural because it is two people or things;
When "either" is followed by a noun as the subject, the predicate verb is regarded as singular because it is any person or thing;
When "neither" is used as the subject, the predicate verb is regarded as singular because there is neither;
When all is followed by a noun as the subject, we should examine whether the noun is countable or uncountable. If it is countable, it is regarded as plural, otherwise it is regarded as singular