What is a nucleon?
- the positively charged particle found in atomic nuclel
- uncharged particle found in atomic nuclel
- either a proton or a neutron
- none of the above

Why is planting a wide variety of plant species better than planting only one type? a) diversity is best for the environment. b) a wide variety would mean less wear and tear on the soil. c) it would lead to desertification prevention. d) combining biological and chemical controls are the conditions of a healthy farm.