那条未经训练的狗对孩子们来说是个危险。

The untrained dog is a ___danger to children.

天黑后独自在公园散步可能有危险。

Walking alone in the park after dark could be a ___danger.

医生警告说，吸烟对你的健康非常危险。

The doctor warns that smoking is a great ___danger to your health.