$1.$ In MapReduce programming, what is the output of the Reduce function?

A$.$ It doesn$$t generate any output ever

B$.$ Key$-$value pairs

C$.$ It is arbitrary and depends on the programmer $2.$How are key$-$value pairs distributed between reduce functions in different computing nodes?

A$.$ A reduce function may receive pairs with different keys and values at once

B$.$ All pairs with the same key are sent to one reduce function

C$.$ All pairs with a same value are sent to one reduce function $3.$

Consider the WordCount example in which you were supposed to count the number of each word in a text. What happens if you set the first letter of each word as the key instead of each word?

Hint: If you are not sure how to do this, the process of the algorithm was described in the video $$How to do a job in parallel$.$

A$.$ MapReduce counts the number of each letter in the text

B$.$ MapReduce still counts the number of each word in the text

C$.$ MapReduce counts the number of words with the same first letter in the text