The hardware company has 40 employees (25 male and 15 female; 10 high school education, 25 undergraduate education and 5 postgraduate education). The company produces 3 kinds of SD cards A, B and C with SD card prices of 50 thousand, 75 thousand and 100 thousand respectively.

a.The education level variable has an interval measurement scale

b.Education level variable has an ordinal measurement scale

c. type of SD card has a ratio measurement scale

d. The education level variable has a nominal measurement scale