Explanation:

- The class has 60 students, with boys being 5/7 times the number of girls.

- Let girls = 7x, which means boys = 5x.

- Total students: $7x+5x=60$; solving gives x = 5. So, girls = 35, boys = 25.

- Girls liking Rose are in the ratio 2:7 of total girls: $(2/7)\times 35=10$.

- Boys who like Sunflower are 60% of girls who like Rose, so boys liking Sunflower = 60% of 10 = 6.

- Girls who like Sunflower are 2.5 times boys liking Sunflower: $2.5\times 6=15$.

- Girls who like Sunflower are 150% of boys liking Lotus, so boys liking Lotus = (15/1.5) = 10.

- Students liking Lotus: Boys = 10, thus girls must be 10 because 35 - 10 - 15 = 10.

- Ratio of boys to girls who like Lotus = 10:10 = 1:1.

The correct answer is Option 4: 1:1