Which of the following is an example of a physical change? A. Sulfur combined with oxygen produces sulfur dioxide
B. Iron exposed to air produces rust.
C. Hydrogen combined with oxygen forms water
D. Liquid nitrogen exposed to air becomes nitrogen gas.

the major pests we deal with are insects, weeds and fungal diseases. a pesticide is a product, whether organic or chemical, used to kill the target pest. there are other techniques gardeners should use that can prevent the severe infestations that make the use of pesticides necessary

i think it's c. if you look search electronic symbol on google and then click on wiki it shows you a