In 1846, astronomers Johann Galle and Heinrich d'Arrest made a groundbreaking discovery while observing the night sky. Using mathematical predictions...

Sentence Structure

• In 1846,
  • astronomers Johann Galle and Heinrich d'Arrest made a groundbreaking discovery
    • while observing the night sky.

• Using mathematical predictions
  • provided by Urbain Le Verrier,
• they [? - identified/are identifying/will identify/will have identified] the planet Neptune
  • for the first time.

• This discovery confirmed the power of mathematical astronomy.

Understanding the Meaning

Let's start from the beginning:

The passage opens with a specific time: 'In 1846'

• This immediately tells us we're talking about something that happened in the past - a historical event.

The first sentence tells us:

• 'astronomers Johann Galle and Heinrich d'Arrest made a groundbreaking discovery while observing the night sky.'
  • Two specific astronomers made a discovery
  • Notice the verb 'made' - this is past tense
  • They made this discovery while observing the sky

Now the second sentence begins:

• 'Using mathematical predictions provided by Urbain Le Verrier'
  • This gives us context - they were using math predictions from another scientist named Le Verrier

Now here's where we need to fill in the blank:

• 'they _____ the planet Neptune for the first time.'

Let's look at our choices:

• We're deciding between different tenses and forms of the verb
• identified (past)
• are identifying (present continuous)
• will identify (future)
• will have identified (future perfect)

What do we know so far?

• The passage starts with 'In 1846' - this happened in the past
• The first sentence uses 'made' - past tense
• We're describing what these astronomers did back in 1846

So we need: past tense - identified

This describes a completed action that happened at a specific point in the past (1846).

Now let's read the final sentence to see the complete picture:

• 'This discovery confirmed the power of mathematical astronomy.'
  • Notice 'confirmed' is also past tense
  • The entire passage is describing a historical event consistently in the past

What do we notice about the structure here?

• The passage establishes a clear time frame: 1846
• All the main verbs describing this discovery need to match that time frame:
  • 'made' a discovery (past)
  • [blank] the planet (past)
  • 'confirmed' the power (past)
• We're describing completed actions from history, so we need past tense throughout.

The correct answer is A. identified - it matches the time context of 1846 and maintains consistent past tense with the other verbs in the passage.

GRAMMAR CONCEPT APPLIED

Matching Verb Tense to Time Context

When a passage establishes a clear time frame (especially with specific dates or time markers), all verbs describing events in that time frame need to use the appropriate tense. Past events require past tense verbs.

The pattern:

• Time marker in past: "In 1846" / "Last year" / "During the 1920s"
• Action that happened then: Use past tense

Examples:

1. With specific date:
   • In 1969, astronauts landed on the moon for the first time.
   • NOT: In 1969, astronauts land / will land on the moon.
2. Multiple verbs in same time frame:
   • The scientists conducted experiments and published their findings in 2010.
   • All verbs stay in past tense because they all happened in 2010
3. In our question:
   • Time marker: "In 1846"
   • First verb: "made" (past)
   • Blank: needs "identified" (past)
   • Third verb: "confirmed" (past)
   • All describe the same historical event, so all use past tense

Key principle: Don't let complex sentence structure distract you from the basic time context. When you see a clear past time marker like "In 1846," you know you need past tense verbs for actions that happened then.