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GMAT TOEIC IELTS TOEFL

TOEFL® Vocabulary Practice

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definition: 
A colourless pungent toxic gas formed by burning sulphur in air.
sentence: 
When fossil fuels burn, carbon dioxide, sulfur dioxide, nitrogen oxides, sooty particles, dioxins, and other pollutants are released into the air and water.
difficulty: 
medium
toefl frequency: 
1