Christopher claims that 4 is not a rotional number because it is not writtwn as a ratio of integers. is he correct? explain why or why not

Christopher is incorrect. The value 4 is a rational number because 
4 = 4/1
We can write 4 as a ratio or fraction of whole numbers. So this is why it's rational.

Note: the denominator or value in the bottom cannot be 0

another note: any whole number or integer is a rational number because we can use the trick shown above. Simply place the value over 1
(other examples: 7 = 7/1, 22 = 22/1, etc)

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.