Update task.md

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Coroutines/Retrofit callback API/task.md

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-In the previous solution, the whole loading logic is moved to the background thread, but that still isn't the best use of
-resources. All of the loading requests go sequentially and the thread is blocked while waiting for the loading result,
-while it could have been occupied by other tasks. Specifically, the thread could start loading another request to
+In the previous solution, the whole loading logic was moved to a background thread. However, this may not be the best use of
+resources. The issue is that all of the loading requests are going sequentially, blocking the thread while waiting for the loading result.
+The thread could, instead, be occupied by other tasks. Specifically, the thread could start loading another request and thus
 receive the entire result earlier.
 
-Handling the data for each repository should then be divided into two parts: loading and processing the
-resulting response. The second _processing_ part should be extracted into a callback.
+The data handling for each repository should be divided into two parts: loading and processing the
+resultant response. The latter _processing_ part should be extracted into a callback.
 
-The loading for each repository can then be started before the result for the previous repository is received (and the
-corresponding callback is called):
+The loading for each repository can then start before the result for the previous repository is received and before the
+corresponding callback is called:
 
 ![Using callback API](images/callbacks.png)
 
 The Retrofit callback API can help achieve this. The `Call.enqueue()` function starts an HTTP request and takes a
-callback as an argument. In this callback, you need to specify what needs to be done after each request.
+callback as an argument. In this callback, you must specify what needs to be done after each request.
 
 Open [src/tasks/Request3Callbacks.kt](course://Coroutines/Retrofit callback API/src/tasks/Request3Callbacks.kt) and see the implementation of `loadContributorsCallbacks()` that uses this API.
 
-* For convenience, this code fragment uses the `onResponse()` extension function declared in the same file. It takes a
+* For convenience, this code fragment uses the `onResponse()` extension function declared in the same file. This function takes a
   lambda as an argument rather than an object expression.
-* The logic for handling the responses is extracted into callbacks: the corresponding lambdas start at lines `#1` and `#2`.
+* The logic to handle the responses is extracted into callbacks: the corresponding lambdas start at lines `#1` and `#2`.
 
 However, the provided solution doesn't work. If you run the program and load contributors by choosing the _CALLBACKS_
-option, you'll see that nothing is shown. However, the tests that immediately return the result pass.
+option, you'll see that nothing is displayed. However, the tests that immediately return the result pass.
 
 ## Task
 
-Rewrite the code in the [src/tasks/Request3Callbacks.kt](course://Coroutines/Retrofit callback API/src/tasks/Request3Callbacks.kt) file so that the loaded list of contributors is shown.
+Rewrite the code in the [src/tasks/Request3Callbacks.kt](course://Coroutines/Retrofit callback API/src/tasks/Request3Callbacks.kt) file so that the loaded list of contributors is displayed.
 
-For a more detailed description, you can look at [this article](https://kotlinlang.org/docs/coroutines-and-channels.html#use-the-retrofit-callback-api)
+For a more detailed description, you can refer to [this article](https://kotlinlang.org/docs/coroutines-and-channels.html#use-the-retrofit-callback-api).