Julia stands on a pair of scales three times in a row. The first time she weighs 69 kilo, the second time 69 kilo, and the third time 69 kilo. Her real weight is 51 kilo. What is the matter with the scales?
A. The pair of scales is not reliable and not valid.
B. The pair of scales is reliable but is not valid.
C. The pair of scales is not reliable but is valid.
D. The pair of scales is reliable and valid.
Answer: B. The pair of scales is reliable but is not valid.