Botanists recognize over fifty different species of sunflower. One species, the silverleaf sunflower, ________ both an early-flowering ecotype that te...

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

• Botanists recognize over fifty different species of sunflower.
• One species,
• the silverleaf sunflower,
• [?] both an early-flowering ecotype
• that tends to grow in coastal areas
• and a late-flowering ecotype
• that grows inland.

Understanding the Meaning

Let's start with the context:

• 'Botanists recognize over fifty different species of sunflower.'
  • This tells us there are many different types of sunflowers.

Now the second sentence focuses on one particular species:

• 'One species, the silverleaf sunflower...'
  • This identifies which species we're talking about.

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

• 'One species, the silverleaf sunflower, ______ both an early-flowering ecotype... and a late-flowering ecotype...'

Let's look at our choices:

• We have different forms of the verb "include"
  • having included
  • including
  • to include
  • includes

What do we need here?

• 'One species' is our subject - it's what the sentence is about
• We need a verb to tell us what this species does
• 'One species' is singular, so we need a singular verb form
• The sentence is stating a current fact about how this species exists

So we need includes - it's the only form that works as a complete verb matching our singular subject 'One species.'

Now let's read the rest to see the complete picture:

• '...both an early-flowering ecotype that tends to grow in coastal areas and a late-flowering ecotype that grows inland.'
  • This tells us what the species includes
  • Two different ecotypes (variations within the species)
  • One flowers early and grows near coasts
  • One flowers late and grows inland

The complete meaning: The silverleaf sunflower is one species that includes two different types - one that flowers early and lives on the coast, and one that flowers late and lives inland.

What do we notice about the structure?

• 'One species' is the subject doing something
• We need the main verb - the action that tells us what the subject does
• This is a straightforward statement of fact, so we need a simple present tense verb
• That verb must agree with our singular subject

The correct answer is D. includes

GRAMMAR CONCEPT APPLIED

Choosing the Right Verb Form to Complete a Sentence

Every complete sentence needs a main verb - the verb that tells what the subject does or is. This main verb must agree with the subject in number (singular subject needs singular verb, plural subject needs plural verb).

Here's the key distinction:

Forms that CAN work as main verbs:

• Simple present: "The species includes two types"
• Simple past: "The species included two types"
• Present with helping verb: "The species has included two types"

Forms that CANNOT work as main verbs alone:

• Participles: "The species including two types" (incomplete - including what about it?)
• Infinitives: "The species to include two types" (incomplete - needs another verb)

In our sentence:

• Subject: "One species" (singular)
• Need: A main verb that agrees with this singular subject
• Answer: "includes" - simple present tense, third person singular
• Result: "One species... includes both an early-flowering ecotype and a late-flowering ecotype"

The sentence makes a statement of fact about how this species currently exists, so the simple present tense "includes" is the correct choice.