In plant cells, numerous structures work together to sustain life. The chloroplast _____ an organelle responsible for photosynthesis, the process...

Sentence Structure

Sentence 1:

• In plant cells,
• numerous structures work together
  • to sustain life.

Sentence 2:

• The chloroplast [is/are/were/have been] an organelle
  • responsible for photosynthesis,
    • the process
      • by which plants convert light energy
        • into chemical energy
          • stored in glucose molecules.

Understanding the Meaning

Let's start reading from the beginning.

The first sentence gives us the context:

• 'In plant cells, numerous structures work together to sustain life.'
• This is telling us that plant cells have many different structures, and they all collaborate to keep the plant alive.

Now the second sentence zooms in on one specific structure:

• 'The chloroplast _____'

Here's where we need to fill in the blank. Let's look at our choices:

• is (singular, present)
• are (plural, present)
• were (plural, past)
• have been (plural, present perfect)

What do we notice?

• Our subject is 'The chloroplast' - this is ONE organelle, so it's singular.
• The choices are asking us to pick between singular and plural verb forms, and also between different tenses.

Based on what we've read:

• 'The chloroplast' is singular (we're talking about one type of organelle)
• So we need a singular verb to match it.
• The sentence is making a definitional statement - explaining what a chloroplast IS (not was, not has been, but simply IS).

So we need: is - the singular present form that agrees with 'The chloroplast.'

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

• 'an organelle responsible for photosynthesis, the process by which plants convert light energy into chemical energy stored in glucose molecules.'

The complete sentence is defining what a chloroplast is:

• It's an organelle (a specialized structure in cells)
• It's responsible for photosynthesis
• Photosynthesis is the process where plants turn light into stored chemical energy

The correct answer is A: is

Grammar Concept Applied

Matching Verbs to Their Subjects (Subject-Verb Agreement)

Verbs must agree with their subjects in number - meaning if you have a singular subject (one thing), you need a singular verb form, and if you have a plural subject (multiple things), you need a plural verb form.

This agreement rule (called subject-verb agreement in grammar terms) works like this:

Singular subject + singular verb:

• The chloroplast is an organelle
• The student works hard
• She has finished

Plural subject + plural verb:

• The chloroplasts are organelles
• The students work hard
• They have finished

In our question:

• Subject: "The chloroplast" = singular (one organelle)
• Verb needed: "is" = singular present form
• This creates proper agreement: "The chloroplast is an organelle"

Key principle: Always identify your true subject first, determine whether it's singular or plural, then choose the verb form that matches in number.