From the information given below, which city has the highest relative humidity?
Urbana, IL: T = 52F, Td = 32F St. Louis, MO: T = 69F, Td = 46F Milwaukee, WI: T = 22F, Td = 21F (difference) Austin, TX: T = 90F, Td = 40F
a.Urbana
b.St. Louis
c.Milwaukee
d.Austin