Roughly 300 nights a year, when the cold air descending from the Andes Mountains meets the warm air rising from...

SOLUTION

Let's begin by understanding the meaning of this sentence. We'll use our understanding of pause points and segment the sentence as shown - understanding and assimilating the meaning of each segment bit by bit!

Sentence Structure

• Roughly 300 nights a year,
  • when the cold air descending from the Andes Mountains
    • meets the warm air rising from Venezuela's coastal Lake Maracaibo,
• the result is a spectacular lightning storm,
  • its strikes so bright, so localized, and so dependable [?]
    • that it has become known as 'Maracaibo's Lighthouse.'

Understanding the Meaning

Let's start from the beginning:

• 'Roughly 300 nights a year'
  • This tells us how often something happens - almost every night.

• 'when the cold air descending from the Andes Mountains meets the warm air rising from Venezuela's coastal Lake Maracaibo'
  • This describes the conditions - when cold mountain air meets warm lake air.

• 'the result is a spectacular lightning storm'
  • This is what happens - a lightning storm occurs.

Now we get more description about the lightning:

• 'its strikes so bright, so localized, and so dependable...'
  • The lightning strikes have three qualities: bright, localized, and dependable
  • Notice the word 'so' repeated before each quality

This is where we have the blank. Let's look at the choices:

• A adds a colon (:)
• B adds a semicolon (;)
• C adds nothing
• D adds a comma (,)

To see what works here, let's read the rest of the sentence and understand what it's saying!

• 'that it has become known as "Maracaibo's Lighthouse"'
  • The lightning has gotten this nickname

Now let's understand what the complete structure is telling us:

• 'so bright, so localized, and so dependable THAT it has become known as...'
  • The lightning is SO [adjective] THAT [result happens]

• This is a 'so...that' construction:
  • The 'so' emphasizes how extreme the qualities are
  • The 'that' introduces the consequence or result of those qualities
  • The lightning is so dependable that it's earned a nickname

What do we notice about the structure here?

• The 'so' adjectives and the 'that' clause work together as one unified pattern
  • They're grammatically connected - the 'that' part depends on the 'so' part
  • You can't separate them

• Think of it like this:
  • 'The coffee was so hot that I burned my tongue'
  • You wouldn't write: 'The coffee was so hot, that I burned my tongue'
  • The 'so...that' construction stays together without punctuation between them

So we need Choice C: dependable (with no punctuation).

The 'that' clause must follow directly after 'dependable' without any punctuation breaking up the 'so...that' construction.

GRAMMAR CONCEPT APPLIED

The "So...That" Construction for Showing Consequence

When you want to show that something is so extreme that it causes a particular result, you use a "so...that" pattern. The key rule is: Don't put any punctuation between the "so" part and the "that" part - they work together as one unified construction.

Pattern:

• So + adjective/adverb + that + clause showing the result

Examples:

1. With single adjective:
   • The movie was so scary that I couldn't sleep
   • NOT: The movie was so scary, that I couldn't sleep
2. With multiple adjectives (like our question):
   • The strikes are so bright, so localized, and so dependable that it has become known as 'Maracaibo's Lighthouse'
   • The three adjectives can have commas between them (bright, localized, and dependable)
   • BUT no punctuation before "that"
3. Why this matters:
   • The "that" clause is directly connected to "so" - it's showing the consequence
   • Any punctuation (comma, semicolon, colon) breaks this connection
   • The construction only works when the parts flow together

In our question:

• "so bright, so localized, and so dependable" sets up the extreme qualities
• "that it has become known as 'Maracaibo's Lighthouse'" shows the result
• No punctuation between them preserves the grammatical relationship