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TOEFL Reading Question Type – Inference

For inference questions, you’ll need to use the stated information in the text to draw a conclusion about unstated information.

There are a couple of common themes among inference questions. For example, they often deal with a “cause and effect” situation by stating the effect of a change. The question will then ask you to identify the cause of that effect.

Similarly, you encounter a partial comparison in the text, which you will then have to complete in the question. Look out for phrases like “now” and “for the first time”, as well as general comparison words like “than” and “relative to.” If you see one of these in the reading, it may be a hint that you’ll have to answer an inference question about it later.

When answering inference questions, be careful not to infer too much. If you assume information that’s not in the passage, you will be wrong. Even though the correct answer will not be stated in the passage, be sure that you can find concrete evidence to support it.

Let’s look at an example (source). For this exercise, context is important. I recommend that you click the link above and read the whole passage; if you don’t want to, here’s a short summary: In this passage, scientists try to figure out why dinosaurs and other animals suddenly went extinct. They believe that the amount of the element Iridium in certain samples of border rock, or rock found just beneath the earth’s surface, may help them answer this question.


10. The paragraph implies that a special explanation of the Iridium in the boundary clay is needed because

(A) the Iridium in microscopic meteorites reaching Earth during the Cretaceous period would have been incorporated into Earth’s core

(B) the Iridium in the boundary clay was deposited much more than a million years ago

(C) the concentration of Iridium in the boundary clay is higher than in microscopic meteorites

(D) the amount of Iridium in the boundary clay is too great to have come from microscopic meteorites during the time the boundary clay was deposited

Answer choice (A) is tempting because it seems related to the second sentence of the paragraph. But earlier in the complete text, (not in the paragraph above) the passage tells us that the Cretaceous period was the time when dinosaurs lived. Meanwhile, a sentence in the paragraph above says that iridium was included in the Earth’s core during the formation of the Earth, when it was “cooling and consolidating.” This was long before the Cretaceous, so we can’t assume that iridium also moved to the core during the Cretaceous.

(B) is incorrect because we’re talking about how long it took for the clay to be deposited (about 1 million years), not how long ago it was deposited. That’s discussed in another paragraph, so you may have had trouble with this one if you didn’t read the whole passage.

(C) doesn’t make any sense. If the iridium in the planet’s rock was deposited by meteorites, then the meteorites must have a higher concentration of iridium than the planet.

(D) “However, other reliable evidence suggests that the deposition of the boundary clay could not have taken one million years.” It would have taken at least a million years to create as high a concentration of iridium as there is, yet scientists are pretty sure that the process took less than that. This is the correct answer, since it is definitely stated in the passage.

The inference is very, very small. Don’t assume too much! The best way to learn exactly how much you can assume is to practice, practice, practice! 🙂