1. Concern for the safety of the two missing teenagers is growing.人们对于两个失踪少年安全状况的担忧与日俱增。

concern：n. 关心，顾虑，担忧例如：Our chief concern at the moment is the weather.（眼前我们最关心的事是天气。）

   2. We are prohibited from smoking in public places.我们被禁止在公共场所抽烟。

prohibit sb. from sth/doing sth.：禁止做某事，阻止做某事例如：Traffic regulations prohibit people from riding bicycles on the sidewalk.（交通规则禁止在人行道上骑自行车。）

   3. The population of the city is close to a million.这个城市的人口接近一百万。

be close to： 接近，靠近例如：My hometown is close to the sea.（我的家乡临近大海。）

   4. This photograph from our wedding is my greatest treasure.这张婚礼上的照片是我最宝贵的财富。

treasure：n. 珍宝，财富；珍藏品例如：Knowledge is a treasure, but practice is the key to it.（知识是一座宝库，而实践就是开启宝库的钥匙。）

问题： She's a green hand. "green hand" means______.

A.老手 B.新手C.绿手D.热手