Help please i not understand

1. the passing of is the basis of heredity. 2. our encode the instructions that define our traits. 3. each of us has thousands of genes, which are made of and reside in our chromosomes. 4. in addition to our genes, the we live in also define our traits. 5. humans have two complete sets of chromosomes. 6. when parents conceive a child, each parent contributes set of chromosomes. 7. every child receives of its chromosomes from the mother and half from the father. 8. this transfer takes place at when the father’s sperm joins the mother’s egg. 9. while most cells in our bodies have two sets of chromosomes, or a total of egg and sperm each have chromosomes. 10. when egg and sperm unite they create a single cell called a 11. each parent contributes complete set of chromosomes to their child. 12. since the parents contribute the chromosomes to each new child, every child inherits a unique set of chromosomes. 13. as a result, every baby will have a combination of traits.

Depending on the organism the number of in a cell may change

Which description provides the best objective summary of the article in the passage?