Question

There is a book in my backpack. book is very heavy. ( insert article)
​

Answer 1

Answer:

There is a book in my backpack , the book i very heavy

Explanation:

Answer 2

Answer:

The book in my backpack is very heavy.

Explanation:

There is a repetition of the word book which should be avoided in a proper English Sentence.

Example:

You would say:

Luke is very handsome and smart.

Rather than,

Luke is very handsome. Luke is very smart.