Along with carbon dioxide concentration and temperature, light intensity affects the chemical reaction rate of ______ as light intensity increases,...

Sentence Structure

• Along with carbon dioxide concentration and temperature, light intensity affects the chemical reaction rate of photosynthesis[?]
  • as light intensity increases, so does the rate at which the reactants (water and carbon dioxide) are converted into their products (glucose and oxygen)

Understanding the Meaning

The sentence starts by setting the context:

• Along with carbon dioxide concentration and temperature
  • These are other factors that affect photosynthesis
• light intensity affects the chemical reaction rate of photosynthesis
  • This is the main claim - light intensity has an effect on how fast photosynthesis happens

This is where we have the blank.

Let's look at the choices:

• We're deciding what punctuation (if any) should come after 'photosynthesis'
• The options are: 'and', a comma, a colon, or nothing

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

The sentence continues:

• as light intensity increases, so does the rate at which the reactants (water and carbon dioxide) are converted into their products (glucose and oxygen)

Now let's really understand what this is telling us:

• as light intensity increases
  • When the light gets brighter or stronger
• so does the rate at which the reactants are converted into their products
  • The speed of conversion also increases
  • The reactants (water and carbon dioxide) become the products (glucose and oxygen) faster

So the complete picture is:

• The first part makes a general statement: light intensity affects photosynthesis's reaction rate
• The second part explains specifically HOW: when light intensity goes up, the reaction rate goes up too

What do we notice about the structure here?

• Both parts are complete thoughts that could stand alone as sentences:
  • 'Light intensity affects the chemical reaction rate of photosynthesis' - complete sentence
  • 'As light intensity increases, so does the rate...' - also a complete sentence
• The second sentence doesn't just add new information - it EXPLAINS the first
  • It shows the specific mechanism of how light intensity affects the rate
  • It's elaborating on what was just stated

When you have two complete sentences where the second one explains or elaborates on the first, you use a colon to show that relationship.

So we need photosynthesis: (Choice C).

Grammar Concept Applied

Using Colons to Introduce Explanations

When you have two complete sentences and the second one explains, elaborates on, or provides examples of the first, you use a colon to connect them. The colon signals to the reader: 'Here's the explanation/elaboration of what I just said.'

This punctuation mark (called a colon in grammar terms) shows a specific relationship - it tells the reader that what follows will provide more detailed information about what came before.

Pattern:

• Complete sentence + colon + complete sentence that explains
• The first part makes a statement
• The second part tells you HOW, WHY, or provides specific details

Examples:

• The study reached a clear conclusion: students who practiced regularly scored 20% higher on the exam.
  • First part: states there was a clear conclusion
  • Second part: tells you what that conclusion was
• The weather forecast proved accurate: temperatures dropped below freezing and snow began falling by midnight.
  • First part: makes a claim about the forecast
  • Second part: provides the specific details that proved it accurate

In our question:

• First part: 'light intensity affects the chemical reaction rate of photosynthesis'
  • Makes a general statement about the relationship
• Second part: 'as light intensity increases, so does the rate at which the reactants are converted into their products'
  • Explains specifically HOW that relationship works - providing the mechanism

The colon is the perfect punctuation here because it signals that the explanation is coming.