Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: 
This sperm is ready to penetrate the membrane of this egg. Notice the difference in size of the sperm and egg. Why is the egg so much larger? The egg contributes all the cytoplasm and organelles to the zygote. The sperm only contributes one set of chromosomes.


Question: Which part of the reproductive process only contributes one set of chromosomes?
sperm
Sperm.