Помогите, пожалуйста, с модальными глаголами

1. High intensity of human activities ______ be the cause of water pollution
a) is able b) may c) ought d) should

2. lanfills are needed for waste that ______ be recycled or safely burned
a) can't b) needn't c) mustn't d) should not

3. Efforts to decrease air pollution _____ be made at the national as well as at international levels
a)are able b) have c) must d) ought

4. Manufacturers _______ make products that have fewer toxic components
a) are able b) need c) ought d) should

5. An effective sewage discharge technology ____ be used to control water quality
a) should b) need c) is able d) has

6. Any large engineering projects _____ harm the earth or the life on it
a) can't b) might not c) mustn't d) needn't