Answer:
The word 'that' is a common word in English that is used in many different manners. Did you notice the use of 'that' in the first sentence? In this case, 'that' was used as a relative pronoun as a compliment. Often 'that' can be used or left out of a sentence entirely.
The word and term 'it' can be used for either a subject or an object in a sentence and can describe any physical or psychological subject and/or object. The genitive form its has been used to refer to human babies and animals