It's asking if the person is available at a specific time. However, most people would say. "Are you available during the following times" "Availability" - You have this when you are available. If you are not available; you do not have this.

"1. It can help the environment to be reduce the use of damaging. /// This is incorrect. 2. It can help the environment by reducing the use of damaging. /// This is almost correct. "It can help the environment by reducing the use of damaging products" Or even better "It can help the environment to reduce the use of damaging products" It depends on what you want to say, exactly. "If you use your car less it will help the environment" 3. GM could give a few huge companies a dangerous monopoly on global food production. /// Correct 4. GM could give a few huge companies to be dangerous monopoly on a global food production. /// Incorrect

"It's true that I had hardly sat down when the doorbell rang"

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