Answer: Option B.
Production Secondary xylem and phloem
Step-by-step explanation:
Cambium in plants is a kind of meristem or layers of dividing cells that produced more xylem and phloem which help to transport water and nutrient to increase plants growth.
When you induced the mutation that doubles the amount of cambium, it increases the production of secondary xylem and phloem ( conducting tissues). These tissues conduct water (xylem) and nutrients (phloem). By transporting water and nutrients, there is increase In plants growth and thickness.