anchor.diff:  :marked
     Now Angular will know to supply an instance of the `HeroService` when it creates a new `AppComponent`. 
   
  -  现在，Angular将会知道，当它创建`AppComponent`实例时，需要先提供一个`HeroService`的实例。
  +  现在，当创建`AppComponent`实例时，Angular 知道需要先提供一个`HeroService`的实例。
   
   .l-sub-section
     :marked
       Learn more about Dependency Injection in the [Dependency Injection](../guide/dependency-injection.html) chapter.
   
  -    要了解关于依赖注入的更多知识，请参见[依赖注入](../guide/dependency-injection.html)一章。
  +    更多依赖注入的信息，见[依赖注入](../guide/dependency-injection.html)。
   
   :marked
     The *injector* does not know yet how to create a `HeroService`. 
     If we ran our code now, Angular would fail with an error:
   
     *注入器*还不知道该如何创建`HeroService`。
  -  如果现在运行我们的代码，Angular就会失败，并报错：
  +  如果现在运行我们的代码，Angular 就会失败，并报错：
   
   code-example(format="nocode").
       EXCEPTION: No provider for HeroService! (AppComponent -> HeroService)
  -    (异常：没有HeroService的提供商！(AppComponent -> HeroService))
  +    (异常：没有 HeroService 的提供商！(AppComponent -> HeroService))
   
   :marked
     We have to teach the *injector* how to make a `HeroService` by registering a `HeroService` **provider**.
  
positive.code: :marked
    ### Use the Hero Service
  
    ### 使用HeroService服务
  
    We're ready to use the `HeroService` in other components starting with our `AppComponent`.
  
    我们可以在多个组件中使用HeroService服务了，先从AppComponent开始。
  
    We begin, as usual, by importing the thing we want to use, the `HeroService`.
  
    通常，我们会从导入要用的东西开始，比如`HeroService`。
  
  +makeExcerpt('toh-4/ts/app/app.component.ts', 'hero-service-import')
  
  
negative.code: :marked
    Here are the code files we discussed in this chapter.
  
    下面是本章讨论过的代码文件：
  
  +makeTabs(`
    toh-4/ts/app/hero.service.ts,
  