Read the following statements and select the correct answer using the code given below Statements  :

a. Summation of ranks method is best suited to measure development levels, when data used are highly skewed.

b. Summation of ranks method is quite simple and easy to handle.

c. Z-Score method is the robust and most reliable among all the methods used to measure levels of development.

d. Use of Principal Component Analysis method should be avoided if inter-correlation among different components of development weak or doubtful.