Вопрос, который вызвал трудности

Помогите преобразовать предложения, содержащие модальные глаголы, в прошедшее время

1. Computers can replace people in dull routine work.
2. The program is a set of instructions that may also include data to be processed.
3. Computer-controlled robots must increase the productivity of industry.
4. They can help in making different decisions.
5. The pupils may work with computers at the lessons.
6. Electric pulses can move at the speed of light.
7. Storage devices must have capacities for the input, output data and programs and for intermediate results.
8. Business minicomputers can perform to 100 million operations per second.
9. In order to solve scientific problems researchers must deal with the language of science — mathematics.
10. Programmers must write application programs in a way that computers can understand.

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Чтобы дать полноценный ответ, был привлечён специалист, который хорошо разбирается в теме «Английский язык». Ваш вопрос звучал так:

Помогите преобразовать предложения, содержащие модальные глаголы, в прошедшее время

1. Computers can replace people in dull routine work.
2. The program is a set of instructions that may also include data to be processed.
3. Computer-controlled robots must increase the productivity of industry.
4. They can help in making different decisions.
5. The pupils may work with computers at the lessons.
6. Electric pulses can move at the speed of light.
7. Storage devices must have capacities for the input, output data and programs and for intermediate results.
8. Business minicomputers can perform to 100 million operations per second.
9. In order to solve scientific problems researchers must deal with the language of science — mathematics.
10. Programmers must write application programs in a way that computers can understand.

После обсуждения с другими специалистами сервиса мы пришли к выводу, что правильный ответ на ваш вопрос будет звучать следующим образом:

1. Computers could replace people in dull routine work.
2. The program was a set of instructions that might also include data to be processed.
3. Computer-controlled robots had to increase the productivity of industry.
4. They could help in making different decisions.
5. The pupils might work with computers at the lessons.
6. Electric pulses could move at the speed of light.
7. Storage devices had to have capacities for the input, output data and programs and for intermediate results.
8. Business minicomputers could perform to 100 million operations per second.
9. In order to solve scientific problems researchers had to deal with the language of science — mathematics.
10. Programmers had to write application programs in a way that computers could understand. 
1. Computers could replace people in dull routine work.
2. The program is a set of instructions that might also include data to be processed.
3. Computer-controlled robots had to increase the productivity of industry.
4. They could help in making different decisions.
5. The pupils might work with computers at the lessons.
6. Electric pulses could move at the speed of light.
7. Storage devices had to have capacities for the input, output data and programs and for intermediate results.
8. Business minicomputers could perform to 100 million operations per second.
9. In order to solve scientific problems researchers had to deal with the language of science — mathematics.
10. Programmers had to write application programs in a way that computers can understand.
Can — couldMay — mightShall — shouldWill — would