The strength of the active chemical in the majority of rooting hormones on the market ranges from 0.1 percent to 0.8 percent.

• A. 0.1 percent to 0.8 percent
• B. 1 percent to 5 percent
• C. 0.01 percent to 0.08 percent
• D. 5 percent to 10 percent

Answer: (A)

Active rooting hormones work by delivering a small amount of auxin to the cutting to kick-start root formation. In most commercial products, the active ingredient (usually indole-3-butyric acid or a similar auxin) is present at about 0.1% to 0.8%. This level hits a balance: it's strong enough to stimulate rooting in a wide range of species, but not so high that it risks burning the plant tissue or causing harm. Higher concentrations, such as 1–5% or 5–10%, are typically too strong for general use and can damage cuttings, while much lower concentrations like 0.01–0.08% often aren’t potent enough to reliably induce rooting in many plants. So, the commonly used range of 0.1% to 0.8% reflects what you’d find in most market products.