Study the following table and answer the question below.
| School name | Total number of students enrolled | Percentage of enrolled students, opted Biology | Ratio of male to female students who opted Biology |
| A | 900 | 30 | 7 ∶ 8 |
| B | 400 | 36 | 9 ∶ 10 |
| C | 1000 | 24 | 5 ∶ 19 |
| D | 800 | 18 | 5 ∶ 7 |
Find the ratio of the number of students who opted biology in school B and school D.
1
1 ∶ 4
2
1 ∶ 2
3
1 ∶ 1
4
2 ∶ 1