根据短文内容，从方框中选择适当的单词填空，使短文意思完整。每空限填一词，每词限用一次。有一个多余选项。
an invention With earned But dollars walking helpful
Bitwalking is 36. invention made by a small company in London. It is an app that brings people rewards just by walking every day. 37. this app, walkers can earn one “Bitwalking dollar” for about 1,000 steps.
Three bitwalking dollars can be 38. by one person per day at most. The money people get from walking can be spent in special online stores, or it can be exchanged for real cash in many places.
One goal behind the app is to make people healthier. It lets people move more and do more exercise in their daily life. 39. the designers also have another goal: to improve people's lives. In many poor countries, people have to walk a long way to go to work, to go to school, or just to get clean water for their families. Workers in the countryside earn less than one dollar a day. By 40. around with the Bitwalking app, they could earn three times more money easily every day.
The company has also set up Bitwalking centers in some poor areas. At the centers, local people will learn how to use the Bitwalking 41. well, and they can also trade their earned dollars for cash there. Bitwalking is really 42. in changing lives!

36. an 37. With 38. earned 39. But 40. walking 41. dollars 42. helpful

36. 空后invention是发音以元音音素开头的可数名词单数，此处表示“一项发明”，填不定冠词an。
37. 此处表达“借助/有了这款应用”，用介词With，句首首字母大写，符合语境。
38. 本句是被动语态，结构为“be+过去分词”，此处表示“被赚取”，填earn的过去分词earned。
39. 前文介绍应用的一个目标是让人们更健康，后文说明设计者还有另一个目标，语义表转折，填But，句首首字母大写。
40. 介词by后接动名词形式，walk around是固定搭配“四处行走”，故填walking。
41. 根据后文“trade their earned dollars for cash”的对应提示，此处指Bitwalking币，填dollars。
42. 固定搭配be helpful in doing sth. 表示“对做某事有帮助”，符合句意，填helpful。