Which is true about soil fumigants..?

• A. On a large scale the chemical is often applied to the soil which is then covered with polythene sheets for a specified time.
• B. On a small scale the chemical is often applied to the soil which is then covered with water seal for a non-specified time
• C. On a large scale the soil surface may be packed following the treatment.
• D. The chemicals are applied a few days before planting.