Which one of the following pesticide is banned now-a-days

Consider the following four measures $(I-I V)$ that could be taken to successfully grow chickpea in an area where bacterial blight is common.

$I.$ Spray with Bordeaux mixture.

$II.$ Control of the insect vector of the disease pathogen.

$III.$ Use of disease-free seeds only.

$I V$. Use of varieties resistant to the disease.

Which of the above measures can control the diseases?

Natural insecticide obtained from neem is

The pesticides used in killing the acquatic pests (including insects) is

Which element plays an important role in nitrogen fixation