首先，我要创建一个抽象基类，用于表示我们要公开的服务。
To begin we create an abstract base class which represents the service we want to expose.
要确保你的儿童照管服务提供者有推行勤洗手或使用醇基洗手液。
Be sure your child care provider promotes frequent hand washing or use of alcohol-based hand sanitizers.
要确保你的儿童照管服务提供者有推行勤洗手或使用醇基洗手液。
Be sure your child care provider promotes frequent hand washing or use of alcohol-based hand sanitizers.
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