Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form cones, or solitary as in yew, Torreya, Ginkgo.
Secondary air pollutants are the ones that are formed as a result of reactions
between primary pollutants and other elements in the atmosphere, such as ozone
BF3 acts as a Lewis acid when it accepts the lone pair of electrons that NH3 donates.
