および／または、およびまたは、and/or, 主語と動詞の一致、subject-verb agreement

and/or、および/または、およびまたは

「日本語の「または」という表現には「および」の意味も含まれている」and/or、翻訳のジェックス｜英文契約書・契約書翻訳

And/or, Wikipedia

Legal criticism[edit]

The phrase has come under criticism in both American and British courts.^[7][8] Judges have called it a "freakish fad", an "accuracy-destroying symbol", and "meaningless".^[7] In a Wisconsin Supreme Court opinion from 1935, Justice Fowler referred to it as "that befuddling, nameless thing, that Janus-faced verbal monstrosity, neither word nor phrase, the child of a brain of someone too lazy or too dull to know what he did mean".^[9] The Kentucky Supreme Court has said it was a "much-condemned conjunctive-disjunctive crutch of sloppy thinkers".^[7] Finally, the Florida Supreme Court has denounced the use of "and/or", stating

...we take our position with that distinguished company of lawyers who have condemned its use. It is one of those inexcusable barbarisms which were sired by indolence and damned by indifference, and has no more place in legal terminology than the vernacular of Uncle Remus has in Holy Writ. I am unable to divine how such senseless jargon becomes current. The coiner of it certainly had no appreciation for terse and concise law English.^[10]

無茶苦茶言われてますｗ

Verbs after "and/or", WordReference.com Language Forums

proximity rule（近所）: "the verb is governed by the element nearest to it."

plural-always-overrides rule（多数決）: "When using 'or', if both elements are singular, then the verb is singular too. However, if one of the elements is plural, then use a plural verb".

ざっくり上記2つの考え方があるようです。

Using a singular or plural verb after "and/or", English Language & Usage

His co-workers and/or his boss was at fault.（近所）

His co-workers and/or his boss were at fault.（多数決）

His co-worker and/or his bosses were at fault.（近所、多数決）

 

ネイティブ間でも色々議論があって基本的にand/or表現は良くないという意見が多いようですが、実際特許では多いし、使うなら"Go with the element closest to the verb, as is common for 'or'" (近所).でいいんじゃないでしょうか？