Subject-verb agreement with a compound subject consisting of multiple gerunds modified by an adverb

Question

In this sentence, we have a compound subject consisting of three gerunds, and this subject clearly takes a plural verb:

Eating, drinking and sleeping are prohibited.

If an adverb is added at the end (so it modifies 'prohibited'), it is still clearly plural:

Eating, drinking and sleeping are prohibited at this location.

But if we add the adverb after the gerunds, it becomes unclear:

Eating, drinking and sleeping at this location ? prohibited.

Should the verb be 'is' or 'are'? Why do both seem grammatical?

Answer 1

Eating, drinking and sleeping at this location is prohibited

might feel acceptable because:

1. the structure is imitating what would be found in the case of participles being reduced into a nounphrase by conjunction reduction
2. "at this location" restrictively and independently modifies three items in a list, which feels quite strange

If, for example, we take the sentence "the houses, shops and banks at this location are old", there's clearly no question of whether we should conjugate for the singular or plural, because there's no possibility of mechanism №1 coming into play, which just leaves us with the slightly awkward feeling conjured by having a modifying phrase that is implied three times but reduced to being written only once because we can do that in English to avoid repetition. In the case of the sentence with participles, because there is an akward feeling and because a way to escape it is provided by the existence of a different structure that is syntactically similar, speakers might naturally use the wrong construction (where the list of participles is reduced into one whole nounphrase (which we can identify by the singular subject-agreement)) just because it feels natural.

This is what I believe is going on here.

Answer 2

"Are."

The subject of the sentence is not altered by the position of adjectives or adverbs.