A
【解析】
试题分析：考查分词做状语。本句中动词“focus one's attention on聚焦于....”与主语you构成主动关系，所以使用现在分词在句中做伴随状语。句意：当你旅行的时候，有时候，你不得不独自去某个地方，这时你总是要聚焦于自己的财产。故A正确。
【名师点睛】
1. 分词或分词短语作状语时，可以表示时间、原因、让步、条件，方式或伴随状况。通常可转换成相应的状语从句；表示方式或伴随状况时可以转换成并列句或非限制性定语从句。例如：
Put into use in April 2000 (=When it was put into use in April 2000), the hotline was meant for residents reporting water and heating supply breakdowns. (2005上海) 分词短语作时间状语
Blamed for the breakdown of the school computer network (=Because she was blamed for the breakdown of the school computer network), Alice was in low spirits. (2006福建) 分词短语作原因状语
Given time (=If he is given time), he’ll make a fist-class tennis player. （03北京）分词短语作条件状语
We often provide our children with toys, footballs or basketballs, thinking that all children like these things. (= and think that all children like these things.) (2006全国3) 分词短语作伴随状语
2. 有时为了强调，分词前可带when, while, if, though, as if, unless等连词一起作状语，以便使句子的意思更清楚、更连贯。例如：
When comparing different cultures, we often pay attention only to the differences without noticing the many similarities. （2006浙江）
Though tired, he still continued reading.
3. 现在分词和过去分词作状语时的用法比较。
不管是现在分词还是过去分词单独作状语，其逻辑主语必须与主句的主语一致。分词作状语通常可转换成一个相应的状语从句或并列句，如果状语分句或并列句中的谓语动词为被动结构，就用过去分词；如果状语分句或并列句中的谓语动词为主动结构，就用现在分词。例如：
When compared with the size of the whole earth , the biggest ocean does not seem big at all. （04湖北）
分词部分相当于When the biggest ocean is compared with the size of the whole earth, 主语与分词是被动关系，所以用过去分词。
When comparing it with the size of the whole earth, we find that the biggest ocean does not seem big at all.
When we compare it with the size of the whole earth... 主语与分词是主动关系, 所以用现在分词。
Faced with a bill for＄10,000(=Because he is faced with a bill for＄10,000), John has taken an extra job. (2006全国2)
Whenever he was asked why he was late for class, he would answer carelessly, always saying the same thing (= and he would say the same thing). （2006江苏）
注意：
1. 现在分词有两种时态：一般式doing和完成式having done。一般式通常表示与主句的谓语动词所表示的动作同时发生或无先后；完成式则强调分词所表示的动作先于谓语动词所表示的动作。 如：
While walking in the street, we met some friends of ours.（同时发生）
Having waited in the queue for half an hour, Tom suddenly realized that he had left his wallet at home. （04北京） （“等待”先于谓语动词“意识到”）
2. 分词的否定式的构成: not +分词。 Not having received a reply, he decided to write again.
考点：考查分词做状语
