Which of the following are reasons for Mendel’s success?

(i) Usage of pure lines or pure breeding varieties

(ii) Consideration of one character at a time

(iii) Maintenance of statistical records of experiments

(iv) Knowledge of linkage and incomplete dominance

(a) (i) and (ii) only

(b) (i), (ii) and (iii)

(c) (i) and (iv) only

(d) (ii), (iii) and (iv)