Which number is the grays among the given choices

The number inches light travels in a year

The number of atoms in your body

The number of solutions to z is not equal to 77

The number of people in the world

It is unclear what "grays" refers to in this context. Can you please provide more information or clarify your question?

Which number is the greatest among the given choices

The number of inches light travels in a year

The number of atoms in your body

The number of solutions to z not equal to 77

The number of people in the world

To determine which number is the greatest among the given choices, we would need specific values for each option. Please provide the numerical values associated with each choice in order to answer your question.