Six Tense Review

Marine biologists _____ the effects of pollution on sea life.

• study

• studies

• studying

• studied

Answer explanation

The correct choice is 'study' because it matches the plural subject 'marine biologists' and is in the present tense, indicating an ongoing action. The other options do not fit grammatically in this context.

Scuba divers _____ underwater to explore coral reefs.

• swim

• swims

• swimming

• swam

Answer explanation

The correct choice is 'swim' because it matches the plural subject 'divers' and is the base form of the verb, suitable for present tense usage in this context.

The environmentalists _____ campaigns to raise awareness about climate change.

• lead

• leads

• leading

• led

Answer explanation

The correct choice is 'lead' because it matches the plural subject 'environmentalists'. 'Leads' is singular, 'leading' is a participle, and 'led' is past tense, which do not fit the present tense context.

The organization _____ beach clean-ups every month.

• organize

• organizes

• organizing

• organized

Answer explanation

The correct choice is 'organizes' because 'organization' is a singular noun, requiring the third-person singular form of the verb. Thus, 'The organization organizes beach clean-ups every month' is grammatically correct.

Many people _____ to protect endangered species.

• volunteer

• volunteers

• volunteering

• volunteered

Answer explanation

The correct choice is 'volunteer' because it fits the sentence structure as a base form verb, indicating a general action that many people engage in to protect endangered species.

Scientists _____ significant progress in ocean conservation.

• have made

• has made

• made

• are making

Answer explanation

The correct choice is 'have made' because 'scientists' is plural, requiring the plural form of the verb. 'Has made' is incorrect for plural subjects, while 'made' and 'are making' do not convey the same completed action.

They _____ many successful clean-up events this year.

• have organized

• has organized

• organized

• are organizing

Answer explanation

The correct choice is 'have organized' because it agrees with the plural subject 'they' and indicates an action completed in the present perfect tense, which is appropriate for events that occurred this year.

I _____ my scuba diving certification recently.

• have obtained

• has obtained

• obtained

• am obtaining

Answer explanation

The correct choice is 'obtained' because it is the simple past tense, indicating a completed action. The sentence refers to a recent event, making 'obtained' the most appropriate option.

Environmental groups _____ raised awareness about plastic waste.

• have

• has

• raised

• are raising

Answer explanation

The correct choice is 'have' because 'environmental groups' is a plural subject, requiring the plural form of the verb. 'Has' is singular, while 'raised' and 'are raising' do not fit the sentence structure.

We _____ participated in several marine conservation projects.

• have

• has

• participated

• are participating

Answer explanation

The correct choice is 'have' because it agrees with the plural subject 'we' in the present perfect tense, indicating ongoing involvement in marine conservation projects.