C. Zinc chloride - Mix 1 pint in 3 gallons of water. Apply at a rate of 3 gallons per 100 square feet of moss area by thoroughly soaking the moss but avoiding runoff. Zinc chloride is corrosive to metals and harmful to plants so dilute all spills by spraying with water. They are noncorrosive and present minimal hazard to people and animals. Even so, oversprays should be thoroughly rinsed.
Some compounds used as weed killers are effective for moss control.
Follow the manufacturer's directions and precautions. When you apply any of these chemicals, they're more effective when the moss is actively growing than when it's in the dormant phase. If you're applying chemicals during the dry season, it's often recommended that you wet the moss first to promote chemical intake. Some of the chemicals listed above will provide minimal protection against future growth, depending on the concentration applied and the exposure conditions. As a whole, however, their long-term effectiveness is limited, and you should consider them only to kill existing growth.