[ Vocabulary ]
single source of air pollution
A. point source
B. nonpoint source
C. ozone
D. conservation

Random Topics:
Adverbs of frequencyTOEFL Adjective and AdverbPassive Voice in Past Simple TenseGrammar Past and Future TenseInfinitives and ING FormsArticles & PrepositionTime and CalendarPast Tense and Past ContinuousWould/would like - affirmative/negativeComparatives and SuperlativesOther quiz:
Tenses › ViewWhile Lan was working as a volunteer in the countryside, she _______ an old friend.
A. met
B. meets
C. had met
D. was meeting
Verb Tenses › View
Select the sentence that is in the past continuous tense.
A. She was reading a book when I called her.
B. She reads a book every night.
Modals › ViewHe ________ ride a bike because he never learned how.
A. can
B. can’t
Modals and Present Tenses › View
Michael and Daniel _____ a lot these days, but _____ their assets.
A. is traveling / can sell
B. cannot travel / is selling
C. can travel / selling
D. are traveling / cannot sell