Consider the following four statements $(a-d)$ regarding the successful cultivation of chickpea in an area where bacterial blight is common:
$(a)$ Spraying of Bordeaux mixture.
$(b)$ Control of the disease vector.
$(c)$ Use of disease-free seeds.
$(d)$ Use of disease-resistant varieties.
Which of the above are the most effective strategies for managing this disease?

• A
  $(b)$ and $(c)$
• B
  $(a)$ and $(b)$
• C
  $(c)$ and $(d)$
• D
  $(a)$ and $(d)$