How do you write this dichotomous key?

4. how does a phospholipid behave in water? the phosphate head does not mix with water; the fatty acid tails do. the phosphate head and the fatty acid tails mix with water. the phosphate head and the fatty acid tails do not mix with water. the phosphate head mixes with water; the fatty acid tails do not.

The influenza virus cause the flu, but not other diseases. why?

What does natural resource management aim at ?