Помогите.

Что такое валентность,окислители,восстановители?

помогите пожалуста выпишите модальные глаголы и их эквиваленты, переведите предложения на русский язык. 1. An effective management structure can reduce stress and direct the productive capacity of employees into business growth and profits. 2. Everyone who earns a salary must pay taxes to the government. 3. Resources may be material things such as food, housing and heating. 4. Russia will have to apply great efforts to rebuild existing industry and agriculture to increase their competitiveness. 5. The state sector industries do not need to compete with other companies because no other company is allowed to provide the same product or service.