Submitted by admin on Mon, 04/21/2014 - 23:54
definition:
(O3))A colourless unstable toxic gas with a pungent odour and powerful oxidizing properties
sentence:
The four usual agents of deterioration in the air apart from oxygen and water are sulphur dioxide, hydrogen sulphide, ozone and nitrogen dioxide
difficulty:
easy
toefl frequency:
2
toefl classification: