IXL | Choose the topic sentence that best captures the main idea

Read the details below.

Aphids produce a sugary liquid eaten by ants, and in return, ants protect aphids from predators.
Pistol shrimp share their seafloor burrows with goby fish, while the goby fish serve as burrow security guards.
While perched on the back of a rhino, an oxpecker bird eats ticks from the rhino's skin and alerts it to signs of danger.

Choose the best topic sentence to introduce a paragraph containing these details.

In nature, two organisms will sometimes provide one another with specialized sources of food that neither organism can obtain independently.

Pairs of species sometimes work together in unexpected ways, benefiting one another through the exchange of food, shelter, or protection.

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Learn with an example

question

Read the details below.

Most synthetic plastics today are made from petroleum, a nonrenewable resource, and can sit in landfills for hundreds of years.
Because bioplastics are made from vegetable oils, cornstarch, or other renewable resources, manufacturers are less likely to face supply shortages.
Some companies are using bioplastics to make utensils, bowls, and food packaging because they break down quickly and safely after being thrown out.

Choose the best topic sentence to introduce a paragraph containing these details.

With their environmental advantages and consistent availability, bioplastics are seen by some as a promising alternative to synthetic plastics.

For decades, synthetic plastics have been the preferred choice because they are inexpensive, versatile, and easy to produce in large quantities.

key idea

A topic sentence states the main, or central, idea of a paragraph and lets the reader know what the paragraph will be about. The rest of the paragraph provides evidence to help support this idea.

When writing a paragraph, be sure to craft a topic sentence that accurately signals what the paragraph will cover. Your topic sentence should not be too broad, too narrow, off topic, or introduce a new detail.

solution

First decide what the details have in common. In this case, they are all about advantages that bioplastics have over synthetic plastics.

This sentence best introduces the details:

green checkmark, With their environmental advantages and consistent availability, bioplastics are seen by some as a promising alternative to synthetic plastics.

This sentence would not be a good topic sentence to introduce the details:

red X symbol, For decades, synthetic plastics have been the preferred choice because they are inexpensive, versatile, and easy to produce in large quantities.

This sentence is off topic. It discusses the benefits of synthetic plastics rather than the benefits of bioplastics.

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