It is an effective biocontrol agent of Parthenium hysterophorus.

Correct option is B

Zygogramma bicolorata is an effective biocontrol agent used to manage the invasive weed Parthenium hysterophorus (Congress grass). This insect feeds on the leaves of the plant, helping to control its spread.
Explanation:
· (a) Neochetina eichhorniae – This is a biocontrol agent for water hyacinth, not for Parthenium hysterophorus.
· (b) Zygogramma bicolorata – Correct answer. This beetle is used to control Parthenium hysterophorus by feeding on its leaves and preventing seed production.
· (c) Cactoblastis cactorum – This is a biocontrol agent used for cactus plants, not Parthenium.
· (d) Dactylopius indicus – This is used for controlling prickly pear cacti, not Parthenium.