Большинство выбрало этот вариант.

Because большинство is grammatically a singular neuter noun in Russian. Even though it refers to many people, Russian normally makes the verb agree with the noun’s grammatical form, not with the real-world number of people.

So:

• большинство = singular, neuter
• past tense verb agrees with it
• therefore: большинство выбрало

This is similar to English the majority chose, where majority is also grammatically singular.

In the past tense, Russian verbs agree with the subject in gender and number.

Past tense forms of выбрать are:

• выбрал — masculine singular
• выбрала — feminine singular
• выбрало — neuter singular
• выбрали — plural

Since большинство is a neuter singular noun, the verb must be выбрало.

The dictionary form is выбрать, which means to choose / to select.

выбрало is:

• past tense
• singular
• neuter
• perfective

So it means that the choosing was completed: it chose / has chosen in the sense of a finished action.

This is an aspect question.

Russian has two aspects:

• выбирать — imperfective
• выбрать — perfective

In this sentence, the action is viewed as a completed result: the majority made its choice. That is why выбрать is used, giving the form выбрало.

Compare:

• Большинство выбирало этот вариант.
  = The majority was choosing / used to choose this option / chose it repeatedly depending on context.

• Большинство выбрало этот вариант.
  = The majority chose this option. Completed action.

You may hear plural agreement in real speech, especially when speakers are thinking about the people inside the group rather than the collective noun itself. However, the standard and safest form here is:

• Большинство выбрало этот вариант.

Why?

Because большинство is grammatically singular neuter.

Plural agreement like выбрали can occur in less formal usage or when the idea of the individual members is especially strong, but for learners, выбрало is the form to learn first.

It is in the accusative case, because it is the direct object of выбрало: it is the thing that was chosen.

For masculine inanimate nouns, the accusative looks the same as the nominative:

• nominative: этот вариант
• accusative: этот вариант

So even though the case is accusative, the form does not change here.

Because вариант is:

• masculine
• singular
• inanimate

For masculine singular inanimate nouns, the accusative form of the adjective/demonstrative matches the nominative:

• nominative: этот вариант
• accusative: этот вариант

If the noun were animate, you would usually see a different accusative form. For example:

• этот человек → accusative этого человека

But вариант is inanimate, so этот stays этот.

It is in the nominative case, because it is the subject of the sentence.

The structure is:

• Большинство — subject, nominative
• выбрало — verb
• этот вариант — direct object, accusative

Yes. Very often большинство is expanded:

• большинство людей
• большинство студентов
• большинство избирателей

Your sentence leaves that noun unstated, because it is understood from context.

So Большинство выбрало этот вариант can mean something like:

• the majority chose this option
• most people chose this option

depending on the situation.

Yes, you could.

Russian word order is more flexible than English because case endings show grammatical roles. The neutral order here is:

• Большинство выбрало этот вариант.

But you can rearrange it for emphasis:

• Этот вариант выбрало большинство.
  = It was this option that the majority chose.

The meaning stays basically the same, but the focus changes.

The stress is:

• больши́нство
• вы́брало
• э́тот
• вариа́нт

So the sentence is pronounced approximately:

• больши́нство вы́брало э́тот вариа́нт

A learner should especially notice:

• большинство has stress on -шин-
• выбрало has stress on the first syllable: вы́-
• вариант has stress on the last syllable: -а́нт

Grammatically, yes: its basic agreement pattern is neuter singular.

That means you normally get things like:

• большинство было
• большинство решило
• большинство выбрало

But in actual usage, especially in more conversational language, speakers sometimes use plural agreement when they are thinking of the individuals in the group. Still, for correct standard grammar, treat большинство as neuter singular.

In this sentence, вариант is best understood as option.

Russian вариант can mean:

• option
• possible version
• variant

In contexts like voting, surveys, tests, or decision-making, этот вариант usually means this option or this choice.

So here it refers to the option that was selected.