Which expression is undefined?

C.

Step-by-step explanation:

you cannot divide by zero, therefore option C is the correct choice because means 4 ÷ 0.

if 0 was the numerator, like in or 0 ÷ 4, the answer would be 0 because 0 divided by 4 is 0. this can be kind of confusing at times, but just remember that as long as 0 is the denominator in a fraction (meaning the 0 is under the fraction bar), the answer will always come out as undefined because you can't divide by 0.

i hope this helps! have a great day <3

it is 28 degrees colder in detroit than philadelphia.

step-by-step explanation:

what number adds to 21

-7 + ? = 21

-7 + 28 = 21

hope it