重点讲解：
1. prop up 支撑；维持；
例句：On the Stock Exchange, aggressive buying propped the market up.
在证券交易所，市场在大量买单的推动下有所上扬HXLdeX9+_u;^5B7。
2. block off 封闭，封住（门、窗或通道）；
例句：Heavy snow has blocked off traffic on the motorways.
大雪阻碍了高速公路上的交通+6HWdkWPftryoicQ%。
3. in advance 提前；事先；
例句：As long as you've paid in advance we won't charge you for delivery.
只要你预先付款，我们就不收你送货费-kRzyiZq[OZ,,Nq。
4. give away 赠送；捐赠；
例句：We have six copies of the book to give away.
这本书我们要赠送6本出去A;M@EL+9rA@|U*VD。
5. as of 在…时；从…起；自…始；
例句：As of now we don't know much about Mars.
目前我们对火星还知之甚少5;!r0FphGcuvX]h5@。
6. stand at 处于（某一水平）；
例句：Your temperature stands at 100°F.
测得你的体温为100华氏度+d+ouB9GL~%kW;。