Correct Answer: Apsara

Solution : According to the data given:
Weight to height ratio of Apeksha = 59 : 1.8 = $\frac{59}{1.8}$ = 32.77
Weight to height ratio of Apsara = 51 : 1.72 = $\frac{51}{1.72}$ = 29.65
Weight to height ratio of Aradhana = 62 : 1.57 = $\frac{62}{1.57}$ = 39.49
Weight to height ratio of Archana = 74 : 1.68 = $\frac{74}{1.68}$ = 44.04
So, the lowest weight-to-height ratio is of Apsara's.
Hence, the correct answer is Apsara.