[Q]: [Ifitgetsempty,ithastoberefilled.]
[A]: [If it gets empty, it has to be refilled.]
[Q]: [Thisensuresaddedsecurity:ifallkeyslooksimilar,itiseasytopressthedooropenerbymistakeandthenthevisitorisinthehouse.]
[A]: [This ensures added security: if all keys look similar, it is easy to press the door opener by mistake and then the visitor is in the house.]
[Q]: [Publichealthisaffectedbyawholerangeofenvironmentalfactors:]
[A]:
[Public health is affected by a whole range of environmental factors:]