We … the meeting indefinitely because we could not form a quorum.

Step 1: Analyze the question The sentence is: "We ____ the meeting indefinitely because we could not form a quorum." We need the word that best fits the situation of a meeting that cannot continue and is put off with no fixed date.

Step 2: Understand the key concepts

• A quorum is the minimum number of members that must be present for a meeting to be valid. If there is no quorum, the meeting cannot proceed with official business.
• Postponed means to delay an event to a later time, usually before it has started.
• Reconvened means to come together again, which is the opposite of what the sentence describes.
• Adjourned means to formally break off a meeting, either to a later time or indefinitely. In formal meeting language, "adjourn indefinitely" (also called adjourn sine die) is the standard collocation.
• Ended is too general. It does not carry the idea that the meeting may resume later.

Step 3: Eliminate options

• B (reconvened): wrong, because it means meeting again.
• D (ended): possible, but it lacks the formal meaning and doesn't fit well with "indefinitely".
• A (postponed): this is close, since the meeting was put off. However, "postponed" usually refers to an event that hasn't started yet. Here the meeting was already in session when the lack of quorum was discovered, and the formal word for suspending a session is "adjourned".
• C (adjourned): the best fit.

Step 4: Answer The correct option is C. adjourned.

Tip: Link adjourn with meetings, courts, and parliament (for example, "The court adjourned the case"). Use postpone for events such as matches, weddings, and exams. When you see "meeting" together with "quorum", think "adjourn".