I am often confused whether to use singular or plural noun. Below I list some examples that I am not sure which one is correct...
- I measured the head width of lizards.
- I measured the head widths of lizards.
- The growth rate of birds is influenced by temperature.
- The growth rates of birds are influenced by temperature.
- The mean heights of this population and that population are different.
- The mean height of this population and that population is different.
EX4: In this example, because (like in other examples) each dog has a nose; dogs [as a group] have (multiple) noses. I want to use "Dogs have noses" but feel it is wrong.
- Dogs have a nose.
- Dogs have noses.
I hope these examples can give some idea what kind of confusions I am having... I want to know some rules that help me identify the correct form.