Definition: You will be given two sentences. One of them is created by paraphrasing the original one, with changes on an aspect, or using synonyms. Your task is to decide what is the difference between two sentences. Types of change are explained below:
 Tense: The verbs in the sentence are changed in tense.
Number: Plural nouns, verbs and pronouns are changed into single ones or the other way around.
Voice: If the verbs are in active voice, they're changed to passive or the other way around.
Adverb: The paraphrase has one adverb or more than the original sentence.
Gender: The paraphrase differs from the original sentence in the gender of the names and pronouns.
Synonym: Some words or phrases of the original sentence are replaced with synonym words or phrases. Changes in the names of people are also considered a synonym change. Classify your answers into Tense, Number, Voice, Adverb, Gender, and Synonym.

Positive Example 1 -
Input: original sentence: Lily spoke to Donna , breaking her silence . paraphrase: Lily is speaking to Donna , breaking her silence .
Output: Tense

Positive Example 2 -
Input: original sentence: I'm sure that my map will show this building ; it is very good . paraphrase: I'm sure that my maps will show these buildings ; they are very good .
Output: Number

Negative Example 1 -
Input: original sentence: The dog chased the cat , which ran up a tree . It waited at the bottom . paraphrase: The dog is chasing the cat , which is running up a tree . It is waiting at the bottom .
Output: Voice

Negative Example 2 -
Input: original sentence: John was doing research in the library when he heard a man humming and whistling . He was very annoyed . paraphrase: John and Steve were doing research in the library when they heard men humming and whistling . They were very annoyed .
Output: Number is changed.

Now complete the following example -
Input: original sentence: Sid explained his theory to Mark but he couldn't understand him . paraphrase: Sid is explaining his theory to Mark but he can't understand him .
Output: 


Answer: Tense